4.1.Application Context

SFrame is a general encryption framing, intended to be used as an E2EElayer over an underlying HBH-encrypted transport such as SRTP or QUIC[RFC3711][MOQ-TRANSPORT].¶

The scale at which SFrame encryption is applied to media determines the overallamount of overhead that SFrame adds to the media stream as well as theengineering complexity involved in integrating SFrame into a particularenvironment. Two patterns are common: using SFrame to encrypt either wholemedia frames (per frame) or individual transport-level media payloads(per packet).¶

For example,Figure 1 shows a typical media sender stack that takes mediafrom some source, encodes it into frames, divides those frames into mediapackets, and then sends those payloads in SRTP packets. The receiver stackperforms the reverse operations, reassembling frames from SRTP packets anddecoding. Arrows indicate two different ways that SFrame protection could beintegrated into this media stack: to encrypt whole frames or individual mediapackets.¶

Applying SFrame per frame in this system offers higher efficiency but mayrequire a more complex integration in environments where depacketization relieson the content of media packets. Applying SFrame per packet avoids thiscomplexity at the cost of higher bandwidth consumption. Some quantitativediscussion of these trade-offs is provided inAppendix B.¶

As noted above, however, SFrame is a general media encapsulation and can beapplied in other scenarios. The important thing is that the sender andreceivers of an SFrame-encrypted object agree on that object's semantics.SFrame does not provide this agreement; it must be arranged by the application.¶

Like SRTP, SFrame does not define how the keys used for SFrame are exchanged bythe parties in the conference. Keys for SFrame might be distributed over anexisting E2E-secure channel (seeSection 5.1) or derived from an E2E-secureshared secret (seeSection 5.2). The key management systemMUST ensure that eachkey used for encrypting media is used by exactly one media sender in order toavoid reuse of nonces.¶

4.2.SFrame Ciphertext

An SFrame ciphertext comprises an SFrame header followed by the output of anAuthenticated Encryption with Associated Data (AEAD) encryption of the plaintext[RFC5116], with the header provided as additionalauthenticated data (AAD).¶

The SFrame header is a variable-length structure described in detail inSection 4.3. The structure of the encrypted data and authentication tagare determined by the AEAD algorithm in use.¶

When SFrame is applied per packet, the payload of each packet will be an SFrameciphertext. When SFrame is applied per frame, the SFrame ciphertextrepresenting an encrypted frame will span several packets, with the headerappearing in the first packet and the authentication tag in the last packet.It is the responsibility of the application to reassemble an encrypted frame fromindividual packets, accounting for packet loss and reordering as necessary.¶

4.3.SFrame Header

The SFrame header specifies two values from which encryption parameters arederived:¶

• A Key ID (KID) that determines which encryption key should be used¶

• A Counter (CTR) that is used to construct the nonce for the encryption¶

ApplicationsMUST ensure that each (KID, CTR) combination is used for exactlyone SFrame encryption operation. A typical approach to achieve this guarantee isoutlined inSection 9.1.¶

The SFrame header has the overall structure shown inFigure 3. Thefirst byte is a "config byte", with the following fields:¶

Extended KID Flag (X, 1 bit):

Indicates if the K field contains the KID or the KID length.¶

KID or KID Length (K, 3 bits):

If the X flag is set to 0, this field contains the KID. If the X flag isset to 1, then it contains the length of the KID, minus one.¶

Extended CTR Flag (Y, 1 bit):

Indicates if the C field contains the CTR or the CTR length.¶

CTR or CTR Length (C, 3 bits):

This field contains the CTR if the Y flag is set to 0, or the CTRlength, minus one, if set to 1.¶

The KID and CTR fields are encoded as compact unsigned integers innetwork (big-endian) byte order. If the value of one of these fields is in therange 0-7, then the value is carried in the corresponding bits of the configbyte (K or C) and the corresponding flag (X or Y) is set to zero. Otherwise,the valueMUST be encoded with the minimum number of bytes required andappended after the config byte, with the KID first and CTR second.The header field (K or C) is set to the number of bytes in the encoded value,minus one. The value 000 represents a length of 1, 001 a length of 2, etc.This allows a 3-bit length field to represent the value lengths 1-8.¶

The SFrame header can thus take one of the four forms shown inFigure 4, depending on which of the X and Y flags are set.¶

4.4.Encryption Schema

SFrame encryption uses an AEAD encryption algorithm and hash function defined bythe cipher suite in use (seeSection 4.5). We will refer to the followingaspects of the AEAD and the hash algorithm below:¶

• AEAD.Encrypt andAEAD.Decrypt - The encryption and decryption functionsfor the AEAD. We follow the convention of RFC 5116[RFC5116] and considerthe authentication tag part of the ciphertext produced byAEAD.Encrypt (asopposed to a separate field as in SRTP[RFC3711]).¶

• AEAD.Nk - The size in bytes of a key for the encryption algorithm¶

• AEAD.Nn - The size in bytes of a nonce for the encryption algorithm¶

• AEAD.Nt - The overhead in bytes of the encryption algorithm (typically thesize of a "tag" that is added to the plaintext)¶

• AEAD.Nka - For cipher suites using the compound AEAD described inSection 4.5.1, the size in bytes of a key for the underlying encryptionalgorithm¶

• Hash.Nh - The size in bytes of the output of the hash function¶

def derive_key_salt(KID, base_key):  sframe_secret = HKDF-Extract("", base_key)  sframe_key_label = "SFrame 1.0 Secret key " + KID + cipher_suite  sframe_key =    HKDF-Expand(sframe_secret, sframe_key_label, AEAD.Nk)  sframe_salt_label = "SFrame 1.0 Secret salt " + KID + cipher_suite  sframe_salt =    HKDF-Expand(sframe_secret, sframe_salt_label, AEAD.Nn)  return sframe_key, sframe_salt

def encrypt(CTR, KID, metadata, plaintext):  sframe_key, sframe_salt = key_store[KID]  # encode_big_endian(x, n) produces an n-byte string encoding the  # integer x in big-endian byte order.  ctr = encode_big_endian(CTR, AEAD.Nn)  nonce = xor(sframe_salt, CTR)  # encode_sframe_header produces a byte string encoding the  # provided KID and CTR values into an SFrame header.  header = encode_sframe_header(CTR, KID)  aad = header + metadata  ciphertext = AEAD.Encrypt(sframe_key, nonce, aad, plaintext)  return header + ciphertext

def decrypt(metadata, sframe_ciphertext):  KID, CTR, header, ciphertext = parse_ciphertext(sframe_ciphertext)  sframe_key, sframe_salt = key_store[KID]  ctr = encode_big_endian(CTR, AEAD.Nn)  nonce = xor(sframe_salt, ctr)  aad = header + metadata  return AEAD.Decrypt(sframe_key, nonce, aad, ciphertext)

4.5.Cipher Suites

Each SFrame session uses a single cipher suite that specifies the followingprimitives:¶

• A hash function used for key derivation¶

• An AEAD encryption algorithm[RFC5116] used for frame encryption, optionallywith a truncated authentication tag¶

This document defines the following cipher suites, with the constants defined inSection 4.4:¶

Numeric identifiers for these cipher suites are defined in the IANA registrycreated inSection 8.1.¶

In the suite names, the length of the authentication tag is indicated bythe last value: "_128" indicates a 128-bit tag, "_80" indicatesan 80-bit tag, "_64" indicates a 64-bit tag, and "_32" indicates a32-bit tag.¶

In a session that uses multiple media streams, different cipher suites might beconfigured for different media streams. For example, in order to conservebandwidth, a session might use a cipher suite with 80-bit tags for video framesand another cipher suite with 32-bit tags for audio frames.¶

def derive_subkeys(sframe_key):  # The encryption key comprises the first Nka bytes  enc_key = sframe_key[..Nka]  # The authentication key comprises Nh remaining bytes  auth_key = sframe_key[Nka..]  return enc_key, auth_key

def truncate(tag, n):  # Take the first `n` bytes of `tag`  return tag[..n]def compute_tag(auth_key, nonce, aad, ct):  aad_len = encode_big_endian(len(aad), 8)  ct_len = encode_big_endian(len(ct), 8)  tag_len = encode_big_endian(Nt, 8)  auth_data = aad_len + ct_len + tag_len + nonce + aad + ct  tag = HMAC(auth_key, auth_data)  return truncate(tag, Nt)def AEAD.Encrypt(key, nonce, aad, pt):  enc_key, auth_key = derive_subkeys(key)  initial_counter = nonce + 0x00000000 # append four zero bytes  ct = AES-CTR.Encrypt(enc_key, initial_counter, pt)  tag = compute_tag(auth_key, nonce, aad, ct)  return ct + tagdef AEAD.Decrypt(key, nonce, aad, ct):  inner_ct, tag = split_ct(ct, tag_len)  enc_key, auth_key = derive_subkeys(key)  candidate_tag = compute_tag(auth_key, nonce, aad, inner_ct)  if !constant_time_equal(tag, candidate_tag):    raise Exception("Authentication Failure")  initial_counter = nonce + 0x00000000 # append four zero bytes  return AES-CTR.Decrypt(enc_key, initial_counter, inner_ct)

5.1.Sender Keys

If the participants in a call have a preexisting E2E-secure channel, they canuse it to distribute SFrame keys. Each client participating in a call generatesa freshbase_key value that it will use to encrypt media. The client then usesthe E2E-secure channel to send their encryption key to the other participants.¶

In this scheme, it is assumed that receivers have a signal outside of SFrame forwhich client has sent a given frame (e.g., an RTP synchronization source (SSRC)). SFrame KIDvalues are then used to distinguish between versions of the sender'sbase_key.¶

KID values in this scheme have two parts: a "key generation" and a "ratchet step".Both are unsigned integers that begin at zero. The key generation incrementseach time the sender distributes a new key to receivers. The ratchet step isincremented each time the sender ratchets their key forward for forward secrecy:¶

base_key[i+1] = HKDF-Expand(                  HKDF-Extract("", base_key[i]),                  "SFrame 1.0 Ratchet", CipherSuite.Nh)

For compactness, we do not send the whole ratchet step. Instead, we send onlyits low-orderR bits, whereR is a value set by the application. Differentsenders may use different values ofR, but each receiver of a given senderneeds to know what value ofR is used by the sender so that they can recognizewhen they need to ratchet (vs. expecting a new key).R effectively defines areordering window, since no more than 2^R ratchet steps can beactive at a given time. The key generation is sent in the remaining64 - Rbits of the KID.¶

KID = (key_generation << R) + (ratchet_step % (1 << R))

The sender signals such a ratchet step update by sending with a KID value inwhich the ratchet step has been incremented. A receiver who receives from asender with a new KID computes the new key as above. The old key may be keptfor some time to allow for out-of-order delivery, but should be deletedpromptly.¶

If a new participant joins in the middle of a session, they will need to receivefrom each sender (a) the current sender key for that sender and (b) the currentKID value for the sender. Evicting a participant requires each sender to senda fresh sender key to all receivers.¶

It is the application's responsibility to decide when sender keys are updated. A senderkey may be updated by sending a newbase_key (updating the key generation) orby hashing the currentbase_key (updating the ratchet step). Ratcheting thekey forward is useful when adding new receivers to an SFrame-based interaction,since it ensures that the new receivers can't decrypt any media encrypted beforethey were added. If a sender wishes to assure the opposite property whenremoving a receiver (i.e., ensuring that the receiver can't decrypt media afterthey are removed), then the sender will need to distribute a new sender key.¶

5.2.MLS

The Messaging Layer Security (MLS) protocol provides group authenticated keyexchange[MLS-ARCH][MLS-PROTO]. Inprinciple, it could be used to instantiate the sender key scheme above, but itcan also be used more efficiently directly.¶

MLS creates a linear sequence of keys, each of which is shared among the membersof a group at a given point in time. When a member joins or leaves the group, anew key is produced that is known only to the augmented or reduced group. Eachstep in the lifetime of the group is known as an "epoch", and each member of thegroup is assigned an "index" that is constant for the time they are in thegroup.¶

To generate keys and nonces for SFrame, we use the MLS exporter function togenerate abase_key value for each MLS epoch. Each member of the group isassigned a set of KID values so that each member has a uniquesframe_key andsframe_salt that it uses to encrypt with. Senders may choose any KID valuewithin their assigned set of KID values, e.g., to allow a single sender to sendmultiple, uncoordinated outbound media streams.¶

base_key = MLS-Exporter("SFrame 1.0 Base Key", "", AEAD.Nk)

For compactness, we do not send the whole epoch number. Instead, we send onlyits low-orderE bits, whereE is a value set by the application.Eeffectively defines a reordering window, since no more than 2^Eepochs can be active at a given time. To handle rollover of the epoch counter,receiversMUST remove an old epoch when a new epoch with the same low-orderE bits is introduced.¶

LetS be the number of bits required to encode a member index in the group,i.e., the smallest value such thatgroup_size <= (1 << S). The sender indexis encoded in theS bits above the epoch. The remaining64 - S - E bits ofthe KID value are acontext value chosen by the sender (context value0 willproduce the shortest encoded KID).¶

KID = (context << (S + E)) + (sender_index << E) + (epoch % (1 << E))

Once an SFrame stack has been provisioned with thesframe_epoch_secret for anepoch, it can compute the required KID values on demand (as well as theresulting SFrame keys/nonces derived from thebase_key and KID) as it needsto encrypt or decrypt for a given member.¶

6.1.Selective Forwarding Units

SFUs (e.g., those described inSection 3.7 of [RFC7667]) receive the media streams from each participant and select whichones should be forwarded to each of the other participants. There are severalapproaches for stream selection, but in general, the SFU needs to accessmetadata associated with each frame and modify the RTP information of the incomingpackets when they are transmitted to the received participants.¶

This section describes how these normal SFU modes of operation interact with theE2EE provided by SFrame.¶

6.2.Video Key Frames

Forward security and post-compromise security require that the E2EE keys (base keys)are updated any time a participant joins or leaves the call.¶

The key exchange happens asynchronously and on a different path than the SFU signalingand media. So it may happen that when a new participant joins the call and theSFU side requests a key frame, the sender generates the E2EE framewith a key that is not known by the receiver, so it will be discarded. When the senderupdates his sending key with the new key, it will send it in a non-key frame, sothe receiver will be able to decrypt it, but not decode it.¶

The new receiver will then re-request a key frame, but due to sender and SFUpolicies, that new key frame could take some time to be generated.¶

If the sender sends a key frame after the new E2EE key is in use, the timerequired for the new participant to display the video is minimized.¶

Note that this issue does not arise for media streams that do not havedependencies among frames, e.g., audio streams. In these streams, each frame isindependently decodable, so a frame never depends on another frame that might beon the other side of a key rotation.¶

6.3.Partial Decoding

Some codecs support partial decoding, where individual packets can be decodedwithout waiting for the full frame to arrive. When SFrame is applied per frame,partial decoding is not possible because the decoder cannot access data until an entireframe has arrived and has been decrypted.¶

7.1.No Header Confidentiality

SFrame provides integrity protection to the SFrame header (the KID andCTR values), but it does not provide confidentiality protection. Parties thatcan observe the SFrame header may learn, for example, which parties are sendingSFrame payloads (from KID values) and at what rates (from CTR values). In caseswhere SFrame is used for end-to-end security on top of hop-by-hop protections(e.g., running over SRTP as described inAppendix B.5), the hop-by-hop securitymechanisms provide confidentiality protection of the SFrame header between hops.¶

7.2.No Per-Sender Authentication

SFrame does not provide per-sender authentication of media data. Any sender ina session can send media that will be associated with any other sender. This isbecause SFrame uses symmetric encryption to protect media data, so that anyreceiver also has the keys required to encrypt packets for the sender.¶

7.3.Key Management

The specifics of key management are beyond the scope of this document. However, every clientSHOULD change their keys when new clients join or leave the call for forwardsecrecy and post-compromise security.¶

7.4.Replay

The handling of replay is out of the scope of this document. However, sendersMUST reject requests to encrypt multiple times with the same key and noncesince several AEAD algorithms fail badly in such cases (see, e.g.,Section 5.1.1 of [RFC5116]).¶

7.5.Risks Due to Short Tags

The SFrame cipher suites based on AES-CTR allow for the use of shortauthentication tags, which bring a higher risk that an attacker will beable to cause an SFrame receiver to accept an SFrame ciphertext of theattacker's choosing.¶

Assuming that the authentication properties of the cipher suite are robust, theonly attack that an attacker can mount is an attempt to find an acceptable(ciphertext, tag) combination through brute force. Such a brute-force attackwill have an expected success rate of the following form:¶

attacker_success_rate = attempts_per_second / 2^(8*Nt)¶

For example, a gigabit Ethernet connection is able to transmit roughly 2²⁰packets per second. If an attacker saturated such a link with guesses against a32-bit authentication tag (Nt=4), then the attacker would succeed on averageroughly once every 2¹² seconds, or about once an hour.¶

In a typical SFrame usage in a real-time media application, there are a fewapproaches to mitigating this risk:¶

• Receivers only accept SFrame ciphertexts over HBH-secure channels (e.g., SRTPsecurity associations or QUIC connections). If this is the case, only anentity that is part of such a channel can mount the above attack.¶

• The expected packet rate for a media stream is very predictable (and typicallyfar lower than the above example). On the one hand, attacks at this rate willsucceed even less often than the high-rate attack described above. On theother hand, the application may use an elevated packet arrival rate as asignal of a brute-force attack. This latter approach is common in othersettings, e.g., mitigating brute-force attacks on passwords.¶

• Media applications typically do not provide feedback to media senders as towhich media packets failed to decrypt. When media-quality feedbackmechanisms are used, decryption failures will typically appear as packetlosses, but only at an aggregate level.¶

• Anti-replay mechanisms (seeSection 7.4) prevent the attacker from reusingvalid ciphertexts (either observed or guessed by the attacker). A receiverapplying anti-replay controls will only accept one valid plaintext per CTRvalue. Since the CTR value is covered by SFrame authentication, an attackerhas to do a fresh search for a valid tag for every forged ciphertext, even ifthe encrypted content is unchanged. In other words, when the above brute-forceattack succeeds, it only allows the attacker to send a single SFrameciphertext; the ciphertext cannot be reused because either it will have thesame CTR value and be discarded as a replay, or else it will have a differentCTR value and its tag will no longer be valid.¶

Nonetheless, without these mitigations, an application that makes use of shorttags will be at heightened risk of forgery attacks. In many cases, it issimpler to use full-size tags and tolerate slightly higher bandwidth usagerather than to add the additional defenses necessary to safely use short tags.¶

8.1.SFrame Cipher Suites

The "SFrame Cipher Suites" registry lists identifiers for SFrame cipher suites as defined inSection 4.5. The cipher suite field is two bytes wide, so the valid ciphersuites are in the range 0x0000 to 0xFFFF. Except as noted below, assignments are madevia the Specification Required policy[RFC8126].¶

The registration template is as follows:¶

• Value: The numeric value of the cipher suite¶

• Name: The name of the cipher suite¶

• Recommended: Whether support for this cipher suite is recommended by the IETF.Valid values are "Y", "N", and "D" as described inSection 17.1 of [MLS-PROTO]. The default value of the "Recommended" column is "N". Setting theRecommended item to "Y" or "D", or changing an item whose current value is "Y"or "D", requires Standards Action[RFC8126].¶

• Reference: The document where this cipher suite is defined¶

• Change Controller: Who is authorized to update the row in the registry¶

Initial contents:¶

9.1.Header Value Uniqueness

ApplicationsMUST ensure that each (base_key, KID, CTR) combination is usedfor at most one SFrame encryption operation. This ensures that the (key, nonce)pairs used by the underlying AEAD algorithm are never reused. Typically this isdone by assigning each sender a KID or set of KIDs, then having each sender usethe CTR field as a monotonic counter, incrementing for each plaintext that isencrypted. In addition to its simplicity, this scheme minimizes overhead bykeeping CTR values as small as possible.¶

In applications where an SFrame context might be written to persistent storage,this context needs to include the last-used CTR value. When the context is usedlater, the application should use the stored CTR value to determine the next CTRvalue to be used in an encryption operation, and then write the next CTR valueback to storage before using the CTR value for encryption. Storing the CTRvalue before usage (vs. after) helps ensure that a storage failure will notcause reuse of the same (base_key, KID, CTR) combination.¶

9.2.Key Management Framework

The application is responsible for provisioning SFrame with a mapping of KID values tobase_key values and the resulting keys and salts. More importantly, theapplication specifies which KID values are used for which purposes (e.g., bywhich senders). An application's KID assignment strategyMUST be structured toassure the non-reuse properties discussed inSection 9.1.¶

The application is also responsible for defining a rotation schedule for keys. Forexample, one application might have an ephemeral group for every call and keeprotating keys when endpoints join or leave the call, while another applicationcould have a persistent group that can be used for multiple calls and simplyderives ephemeral symmetric keys for a specific call.¶

It should be noted that KID values are not encrypted by SFrame and are thusvisible to any application-layer intermediaries that might handle an SFrameciphertext. If there are application semantics included in KID values, thenthis information would be exposed to intermediaries. For example, in the schemeofSection 5.1, the number of ratchet steps per sender is exposed, and inthe scheme ofSection 5.2, the number of epochs and the MLS sender ID of the SFramesender are exposed.¶

9.3.Anti-Replay

It is the responsibility of the application to handle anti-replay. Replay by networkattackers is assumed to be prevented by network-layer facilities (e.g., TLS, SRTP).As mentioned inSection 7.4, sendersMUST reject requests to encrypt multiple timeswith the same key and nonce.¶

It is not mandatory to implement anti-replay on the receiver side. ReceiversMAYapply time- or counter-based anti-replay mitigations. For example,Section 3.3.2 of [RFC3711] specifies a counter-based anti-replay mitigation, whichcould be adapted to use with SFrame, using the CTR field as the counter.¶

9.4.Metadata

Themetadata input to SFrame operations is an opaque byte string specified by the application. Assuch, the application needs to define what information should go in themetadata input and ensure that it is provided to the encryption and decryptionfunctions at the appropriate points. A receiverMUST NOT use SFrame-authenticatedmetadata until after the SFrame decrypt function has authenticated it, unlessthe purpose of such usage is to prepare an SFrame ciphertext for SFramedecryption. Essentially, metadata may be used "upstream of SFrame" in aprocessing pipeline, but only to prepare for SFrame decryption.¶

For example, consider an application where SFrame is used to encrypt audioframes that are sent over SRTP, with some application data included in the RTPheader extension. Suppose the application also includes this application data inthe SFrame metadata, so that the SFU is allowed to read, but not modify, theapplication data. A receiver can use the application data in the RTP headerextension as part of the standard SRTP decryption process since this isrequired to recover the SFrame ciphertext carried in the SRTP payload. However,the receiverMUST NOT use the application data for other purposes before SFramedecryption has authenticated the application data.¶

B.1.Assumptions

In the below calculations, we make conservative assumptions about SFrameoverhead so that the overhead amounts we compute here are likely to be an upperbound of those seen in practice.¶

In total, then, we assume that each SFrame encryption will add 22 bytes ofoverhead.¶

We consider two scenarios: applying SFrame per frame and per packet. In eachscenario, we compute the SFrame overhead in absolute terms (kbps) and as apercentage of the base bandwidth.¶

B.2.Audio

In audio streams, there is typically a one-to-one relationship between framesand packets, so the overhead is the same whether one uses SFrame at a per-packetor per-frame level.¶

Table 4 considers three scenarios that are based on recommended configurationsof the Opus codec[RFC6716] (where "fps" stands for "frames per second"):¶

B.3.Video

Video frames can be larger than an MTU and thus are commonly split acrossmultiple frames. Tables5and6show the estimated overhead of encrypting a video stream, where SFrame isapplied per frame and per packet, respectively. The choices of resolution,frames per second, and bandwidth roughly reflect the capabilities ofmodern video codecs across a range from very low to very high quality.¶

In the per-frame case, the SFrame percentage overhead approaches zero as thequality of the video improves since bandwidth is driven more by picture sizethan frame rate. In the per-packet case, the SFrame percentage overheadapproaches the ratio between the SFrame overhead per packet and the MTU (here 22bytes of SFrame overhead divided by an assumed 1200-byte MTU, or about 1.8%).¶

B.4.Conferences

Real conferences usually involve several audio and video streams. The overheadof SFrame in such a conference is the aggregate of the overhead across all theindividual streams. Thus, while SFrame incurs a large percentage overhead on anaudio stream, if the conference also involves a video stream, then the audiooverhead is likely negligible relative to the overall bandwidth of theconference.¶

For example,Table 7 shows the overhead estimates for a two-personconference where one person is sending low-quality media and the other issending high-quality media. (And we assume that SFrame is applied per frame.) Thevideo streams dominate the bandwidth at the SFU, so the total bandwidth overheadis only around 1%.¶

B.5.SFrame over RTP

SFrame is a generic encapsulation format, but many of the applications in whichit is likely to be integrated are based on RTP. This section discusses how anintegration between SFrame and RTP could be done, and some of the challengesthat would need to be overcome.¶

As discussed inSection 4.1, there are two natural patterns forintegrating SFrame into an application: applying SFrame per frame or per packet.In RTP-based applications, applying SFrame per packet means that the payload ofeach RTP packet will be an SFrame ciphertext, starting with an SFrame header, asshown inFigure 11. Applying SFrame per frame means that differentRTP payloads will have different formats: The first payload of a frame willcontain the SFrame headers, and subsequent payloads will contain further chunksof the ciphertext, as shown inFigure 12.¶

In order for these media payloads to be properly interpreted by receivers,receivers will need to be configured to know which of the above schemes thesender has applied to a given sequence of RTP packets. SFrame does not providea mechanism for distributing this configuration information. In applicationsthat use SDP for negotiating RTP media streams[RFC8866], an appropriateextension to SDP could provide this function.¶

Applying SFrame per frame also requires that packetization and depacketizationbe done in a generic manner that does not depend on the media content of thepackets, since the content being packetized or depacketized will be opaqueciphertext (except for the SFrame header). In order for such a genericpacketization scheme to work interoperably, one would have to be defined, e.g.,as proposed in[RTP-PAYLOAD].¶

C.1.Header Encoding/Decoding

For each case, we provide:¶

• kid: A KID value¶

• ctr: A CTR value¶

• header: An encoded SFrame header¶

An implementation should verify that:¶

• Encoding a header with the KID and CTR results in the provided header value¶

• Decoding the provided header value results in the provided KID and CTR values¶

kid: 0x0000000000000000ctr: 0x0000000000000000header: 00

kid: 0x0000000000000000ctr: 0x0000000000000001header: 01

kid: 0x0000000000000000ctr: 0x00000000000000ffheader: 08ff

kid: 0x0000000000000000ctr: 0x0000000000000100header: 090100

kid: 0x0000000000000000ctr: 0x000000000000ffffheader: 09ffff

kid: 0x0000000000000000ctr: 0x0000000000010000header: 0a010000

kid: 0x0000000000000000ctr: 0x0000000000ffffffheader: 0affffff

kid: 0x0000000000000000ctr: 0x0000000001000000header: 0b01000000

kid: 0x0000000000000000ctr: 0x00000000ffffffffheader: 0bffffffff

kid: 0x0000000000000000ctr: 0x0000000100000000header: 0c0100000000

kid: 0x0000000000000000ctr: 0x000000ffffffffffheader: 0cffffffffff

kid: 0x0000000000000000ctr: 0x0000010000000000header: 0d010000000000

kid: 0x0000000000000000ctr: 0x0000ffffffffffffheader: 0dffffffffffff

kid: 0x0000000000000000ctr: 0x0001000000000000header: 0e01000000000000

kid: 0x0000000000000000ctr: 0x00ffffffffffffffheader: 0effffffffffffff

kid: 0x0000000000000000ctr: 0x0100000000000000header: 0f0100000000000000

kid: 0x0000000000000000ctr: 0xffffffffffffffffheader: 0fffffffffffffffff

kid: 0x0000000000000001ctr: 0x0000000000000000header: 10

kid: 0x0000000000000001ctr: 0x0000000000000001header: 11

kid: 0x0000000000000001ctr: 0x00000000000000ffheader: 18ff

kid: 0x0000000000000001ctr: 0x0000000000000100header: 190100

kid: 0x0000000000000001ctr: 0x000000000000ffffheader: 19ffff

kid: 0x0000000000000001ctr: 0x0000000000010000header: 1a010000

kid: 0x0000000000000001ctr: 0x0000000000ffffffheader: 1affffff

kid: 0x0000000000000001ctr: 0x0000000001000000header: 1b01000000

kid: 0x0000000000000001ctr: 0x00000000ffffffffheader: 1bffffffff

kid: 0x0000000000000001ctr: 0x0000000100000000header: 1c0100000000

kid: 0x0000000000000001ctr: 0x000000ffffffffffheader: 1cffffffffff

kid: 0x0000000000000001ctr: 0x0000010000000000header: 1d010000000000

kid: 0x0000000000000001ctr: 0x0000ffffffffffffheader: 1dffffffffffff

kid: 0x0000000000000001ctr: 0x0001000000000000header: 1e01000000000000

kid: 0x0000000000000001ctr: 0x00ffffffffffffffheader: 1effffffffffffff

kid: 0x0000000000000001ctr: 0x0100000000000000header: 1f0100000000000000

kid: 0x0000000000000001ctr: 0xffffffffffffffffheader: 1fffffffffffffffff

kid: 0x00000000000000ffctr: 0x0000000000000000header: 80ff

kid: 0x00000000000000ffctr: 0x0000000000000001header: 81ff

kid: 0x00000000000000ffctr: 0x00000000000000ffheader: 88ffff

kid: 0x00000000000000ffctr: 0x0000000000000100header: 89ff0100

kid: 0x00000000000000ffctr: 0x000000000000ffffheader: 89ffffff

kid: 0x00000000000000ffctr: 0x0000000000010000header: 8aff010000

kid: 0x00000000000000ffctr: 0x0000000000ffffffheader: 8affffffff

kid: 0x00000000000000ffctr: 0x0000000001000000header: 8bff01000000

kid: 0x00000000000000ffctr: 0x00000000ffffffffheader: 8bffffffffff

kid: 0x00000000000000ffctr: 0x0000000100000000header: 8cff0100000000

kid: 0x00000000000000ffctr: 0x000000ffffffffffheader: 8cffffffffffff

kid: 0x00000000000000ffctr: 0x0000010000000000header: 8dff010000000000

kid: 0x00000000000000ffctr: 0x0000ffffffffffffheader: 8dffffffffffffff

kid: 0x00000000000000ffctr: 0x0001000000000000header: 8eff01000000000000

kid: 0x00000000000000ffctr: 0x00ffffffffffffffheader: 8effffffffffffffff

kid: 0x00000000000000ffctr: 0x0100000000000000header: 8fff0100000000000000

kid: 0x00000000000000ffctr: 0xffffffffffffffffheader: 8fffffffffffffffffff

kid: 0x0000000000000100ctr: 0x0000000000000000header: 900100

kid: 0x0000000000000100ctr: 0x0000000000000001header: 910100

kid: 0x0000000000000100ctr: 0x00000000000000ffheader: 980100ff

kid: 0x0000000000000100ctr: 0x0000000000000100header: 9901000100

kid: 0x0000000000000100ctr: 0x000000000000ffffheader: 990100ffff

kid: 0x0000000000000100ctr: 0x0000000000010000header: 9a0100010000

kid: 0x0000000000000100ctr: 0x0000000000ffffffheader: 9a0100ffffff

kid: 0x0000000000000100ctr: 0x0000000001000000header: 9b010001000000

kid: 0x0000000000000100ctr: 0x00000000ffffffffheader: 9b0100ffffffff

kid: 0x0000000000000100ctr: 0x0000000100000000header: 9c01000100000000

kid: 0x0000000000000100ctr: 0x000000ffffffffffheader: 9c0100ffffffffff

kid: 0x0000000000000100ctr: 0x0000010000000000header: 9d0100010000000000

kid: 0x0000000000000100ctr: 0x0000ffffffffffffheader: 9d0100ffffffffffff

kid: 0x0000000000000100ctr: 0x0001000000000000header: 9e010001000000000000

kid: 0x0000000000000100ctr: 0x00ffffffffffffffheader: 9e0100ffffffffffffff

kid: 0x0000000000000100ctr: 0x0100000000000000header: 9f01000100000000000000

kid: 0x0000000000000100ctr: 0xffffffffffffffffheader: 9f0100ffffffffffffffff

kid: 0x000000000000ffffctr: 0x0000000000000000header: 90ffff

kid: 0x000000000000ffffctr: 0x0000000000000001header: 91ffff

kid: 0x000000000000ffffctr: 0x00000000000000ffheader: 98ffffff

kid: 0x000000000000ffffctr: 0x0000000000000100header: 99ffff0100

kid: 0x000000000000ffffctr: 0x000000000000ffffheader: 99ffffffff

kid: 0x000000000000ffffctr: 0x0000000000010000header: 9affff010000

kid: 0x000000000000ffffctr: 0x0000000000ffffffheader: 9affffffffff

kid: 0x000000000000ffffctr: 0x0000000001000000header: 9bffff01000000

kid: 0x000000000000ffffctr: 0x00000000ffffffffheader: 9bffffffffffff

kid: 0x000000000000ffffctr: 0x0000000100000000header: 9cffff0100000000

kid: 0x000000000000ffffctr: 0x000000ffffffffffheader: 9cffffffffffffff

kid: 0x000000000000ffffctr: 0x0000010000000000header: 9dffff010000000000

kid: 0x000000000000ffffctr: 0x0000ffffffffffffheader: 9dffffffffffffffff

kid: 0x000000000000ffffctr: 0x0001000000000000header: 9effff01000000000000

kid: 0x000000000000ffffctr: 0x00ffffffffffffffheader: 9effffffffffffffffff

kid: 0x000000000000ffffctr: 0x0100000000000000header: 9fffff0100000000000000

kid: 0x000000000000ffffctr: 0xffffffffffffffffheader: 9fffffffffffffffffffff

kid: 0x0000000000010000ctr: 0x0000000000000000header: a0010000

kid: 0x0000000000010000ctr: 0x0000000000000001header: a1010000

kid: 0x0000000000010000ctr: 0x00000000000000ffheader: a8010000ff

kid: 0x0000000000010000ctr: 0x0000000000000100header: a90100000100

kid: 0x0000000000010000ctr: 0x000000000000ffffheader: a9010000ffff

kid: 0x0000000000010000ctr: 0x0000000000010000header: aa010000010000

kid: 0x0000000000010000ctr: 0x0000000000ffffffheader: aa010000ffffff

kid: 0x0000000000010000ctr: 0x0000000001000000header: ab01000001000000

kid: 0x0000000000010000ctr: 0x00000000ffffffffheader: ab010000ffffffff

kid: 0x0000000000010000ctr: 0x0000000100000000header: ac0100000100000000

kid: 0x0000000000010000ctr: 0x000000ffffffffffheader: ac010000ffffffffff

kid: 0x0000000000010000ctr: 0x0000010000000000header: ad010000010000000000

kid: 0x0000000000010000ctr: 0x0000ffffffffffffheader: ad010000ffffffffffff

kid: 0x0000000000010000ctr: 0x0001000000000000header: ae01000001000000000000

kid: 0x0000000000010000ctr: 0x00ffffffffffffffheader: ae010000ffffffffffffff

kid: 0x0000000000010000ctr: 0x0100000000000000header: af0100000100000000000000

kid: 0x0000000000010000ctr: 0xffffffffffffffffheader: af010000ffffffffffffffff

kid: 0x0000000000ffffffctr: 0x0000000000000000header: a0ffffff

kid: 0x0000000000ffffffctr: 0x0000000000000001header: a1ffffff

kid: 0x0000000000ffffffctr: 0x00000000000000ffheader: a8ffffffff

kid: 0x0000000000ffffffctr: 0x0000000000000100header: a9ffffff0100

kid: 0x0000000000ffffffctr: 0x000000000000ffffheader: a9ffffffffff

kid: 0x0000000000ffffffctr: 0x0000000000010000header: aaffffff010000

kid: 0x0000000000ffffffctr: 0x0000000000ffffffheader: aaffffffffffff

kid: 0x0000000000ffffffctr: 0x0000000001000000header: abffffff01000000

kid: 0x0000000000ffffffctr: 0x00000000ffffffffheader: abffffffffffffff

kid: 0x0000000000ffffffctr: 0x0000000100000000header: acffffff0100000000

kid: 0x0000000000ffffffctr: 0x000000ffffffffffheader: acffffffffffffffff

kid: 0x0000000000ffffffctr: 0x0000010000000000header: adffffff010000000000

kid: 0x0000000000ffffffctr: 0x0000ffffffffffffheader: adffffffffffffffffff

kid: 0x0000000000ffffffctr: 0x0001000000000000header: aeffffff01000000000000

kid: 0x0000000000ffffffctr: 0x00ffffffffffffffheader: aeffffffffffffffffffff

kid: 0x0000000000ffffffctr: 0x0100000000000000header: afffffff0100000000000000

kid: 0x0000000000ffffffctr: 0xffffffffffffffffheader: afffffffffffffffffffffff

kid: 0x0000000001000000ctr: 0x0000000000000000header: b001000000

kid: 0x0000000001000000ctr: 0x0000000000000001header: b101000000

kid: 0x0000000001000000ctr: 0x00000000000000ffheader: b801000000ff

kid: 0x0000000001000000ctr: 0x0000000000000100header: b9010000000100

kid: 0x0000000001000000ctr: 0x000000000000ffffheader: b901000000ffff

kid: 0x0000000001000000ctr: 0x0000000000010000header: ba01000000010000

kid: 0x0000000001000000ctr: 0x0000000000ffffffheader: ba01000000ffffff

kid: 0x0000000001000000ctr: 0x0000000001000000header: bb0100000001000000

kid: 0x0000000001000000ctr: 0x00000000ffffffffheader: bb01000000ffffffff

kid: 0x0000000001000000ctr: 0x0000000100000000header: bc010000000100000000

kid: 0x0000000001000000ctr: 0x000000ffffffffffheader: bc01000000ffffffffff

kid: 0x0000000001000000ctr: 0x0000010000000000header: bd01000000010000000000

kid: 0x0000000001000000ctr: 0x0000ffffffffffffheader: bd01000000ffffffffffff

kid: 0x0000000001000000ctr: 0x0001000000000000header: be0100000001000000000000

kid: 0x0000000001000000ctr: 0x00ffffffffffffffheader: be01000000ffffffffffffff

kid: 0x0000000001000000ctr: 0x0100000000000000header: bf010000000100000000000000

kid: 0x0000000001000000ctr: 0xffffffffffffffffheader: bf01000000ffffffffffffffff

kid: 0x00000000ffffffffctr: 0x0000000000000000header: b0ffffffff

kid: 0x00000000ffffffffctr: 0x0000000000000001header: b1ffffffff

kid: 0x00000000ffffffffctr: 0x00000000000000ffheader: b8ffffffffff

kid: 0x00000000ffffffffctr: 0x0000000000000100header: b9ffffffff0100

kid: 0x00000000ffffffffctr: 0x000000000000ffffheader: b9ffffffffffff

kid: 0x00000000ffffffffctr: 0x0000000000010000header: baffffffff010000

kid: 0x00000000ffffffffctr: 0x0000000000ffffffheader: baffffffffffffff

kid: 0x00000000ffffffffctr: 0x0000000001000000header: bbffffffff01000000

kid: 0x00000000ffffffffctr: 0x00000000ffffffffheader: bbffffffffffffffff

kid: 0x00000000ffffffffctr: 0x0000000100000000header: bcffffffff0100000000

kid: 0x00000000ffffffffctr: 0x000000ffffffffffheader: bcffffffffffffffffff

kid: 0x00000000ffffffffctr: 0x0000010000000000header: bdffffffff010000000000

kid: 0x00000000ffffffffctr: 0x0000ffffffffffffheader: bdffffffffffffffffffff

kid: 0x00000000ffffffffctr: 0x0001000000000000header: beffffffff01000000000000

kid: 0x00000000ffffffffctr: 0x00ffffffffffffffheader: beffffffffffffffffffffff

kid: 0x00000000ffffffffctr: 0x0100000000000000header: bfffffffff0100000000000000

kid: 0x00000000ffffffffctr: 0xffffffffffffffffheader: bfffffffffffffffffffffffff

kid: 0x0000000100000000ctr: 0x0000000000000000header: c00100000000

kid: 0x0000000100000000ctr: 0x0000000000000001header: c10100000000

kid: 0x0000000100000000ctr: 0x00000000000000ffheader: c80100000000ff

kid: 0x0000000100000000ctr: 0x0000000000000100header: c901000000000100

kid: 0x0000000100000000ctr: 0x000000000000ffffheader: c90100000000ffff

kid: 0x0000000100000000ctr: 0x0000000000010000header: ca0100000000010000

kid: 0x0000000100000000ctr: 0x0000000000ffffffheader: ca0100000000ffffff

kid: 0x0000000100000000ctr: 0x0000000001000000header: cb010000000001000000

kid: 0x0000000100000000ctr: 0x00000000ffffffffheader: cb0100000000ffffffff

kid: 0x0000000100000000ctr: 0x0000000100000000header: cc01000000000100000000

kid: 0x0000000100000000ctr: 0x000000ffffffffffheader: cc0100000000ffffffffff

kid: 0x0000000100000000ctr: 0x0000010000000000header: cd0100000000010000000000

kid: 0x0000000100000000ctr: 0x0000ffffffffffffheader: cd0100000000ffffffffffff

kid: 0x0000000100000000ctr: 0x0001000000000000header: ce010000000001000000000000

kid: 0x0000000100000000ctr: 0x00ffffffffffffffheader: ce0100000000ffffffffffffff

kid: 0x0000000100000000ctr: 0x0100000000000000header: cf01000000000100000000000000

kid: 0x0000000100000000ctr: 0xffffffffffffffffheader: cf0100000000ffffffffffffffff

kid: 0x000000ffffffffffctr: 0x0000000000000000header: c0ffffffffff

kid: 0x000000ffffffffffctr: 0x0000000000000001header: c1ffffffffff

kid: 0x000000ffffffffffctr: 0x00000000000000ffheader: c8ffffffffffff

kid: 0x000000ffffffffffctr: 0x0000000000000100header: c9ffffffffff0100

kid: 0x000000ffffffffffctr: 0x000000000000ffffheader: c9ffffffffffffff

kid: 0x000000ffffffffffctr: 0x0000000000010000header: caffffffffff010000

kid: 0x000000ffffffffffctr: 0x0000000000ffffffheader: caffffffffffffffff

kid: 0x000000ffffffffffctr: 0x0000000001000000header: cbffffffffff01000000

kid: 0x000000ffffffffffctr: 0x00000000ffffffffheader: cbffffffffffffffffff

kid: 0x000000ffffffffffctr: 0x0000000100000000header: ccffffffffff0100000000

kid: 0x000000ffffffffffctr: 0x000000ffffffffffheader: ccffffffffffffffffffff

kid: 0x000000ffffffffffctr: 0x0000010000000000header: cdffffffffff010000000000

kid: 0x000000ffffffffffctr: 0x0000ffffffffffffheader: cdffffffffffffffffffffff

kid: 0x000000ffffffffffctr: 0x0001000000000000header: ceffffffffff01000000000000

kid: 0x000000ffffffffffctr: 0x00ffffffffffffffheader: ceffffffffffffffffffffffff

kid: 0x000000ffffffffffctr: 0x0100000000000000header: cfffffffffff0100000000000000

kid: 0x000000ffffffffffctr: 0xffffffffffffffffheader: cfffffffffffffffffffffffffff

kid: 0x0000010000000000ctr: 0x0000000000000000header: d0010000000000

kid: 0x0000010000000000ctr: 0x0000000000000001header: d1010000000000

kid: 0x0000010000000000ctr: 0x00000000000000ffheader: d8010000000000ff

kid: 0x0000010000000000ctr: 0x0000000000000100header: d90100000000000100

kid: 0x0000010000000000ctr: 0x000000000000ffffheader: d9010000000000ffff

kid: 0x0000010000000000ctr: 0x0000000000010000header: da010000000000010000

kid: 0x0000010000000000ctr: 0x0000000000ffffffheader: da010000000000ffffff

kid: 0x0000010000000000ctr: 0x0000000001000000header: db01000000000001000000

kid: 0x0000010000000000ctr: 0x00000000ffffffffheader: db010000000000ffffffff

kid: 0x0000010000000000ctr: 0x0000000100000000header: dc0100000000000100000000

kid: 0x0000010000000000ctr: 0x000000ffffffffffheader: dc010000000000ffffffffff

kid: 0x0000010000000000ctr: 0x0000010000000000header: dd010000000000010000000000

kid: 0x0000010000000000ctr: 0x0000ffffffffffffheader: dd010000000000ffffffffffff

kid: 0x0000010000000000ctr: 0x0001000000000000header: de01000000000001000000000000

kid: 0x0000010000000000ctr: 0x00ffffffffffffffheader: de010000000000ffffffffffffff

kid: 0x0000010000000000ctr: 0x0100000000000000header: df0100000000000100000000000000

kid: 0x0000010000000000ctr: 0xffffffffffffffffheader: df010000000000ffffffffffffffff

kid: 0x0000ffffffffffffctr: 0x0000000000000000header: d0ffffffffffff

kid: 0x0000ffffffffffffctr: 0x0000000000000001header: d1ffffffffffff

kid: 0x0000ffffffffffffctr: 0x00000000000000ffheader: d8ffffffffffffff

kid: 0x0000ffffffffffffctr: 0x0000000000000100header: d9ffffffffffff0100

kid: 0x0000ffffffffffffctr: 0x000000000000ffffheader: d9ffffffffffffffff

kid: 0x0000ffffffffffffctr: 0x0000000000010000header: daffffffffffff010000

kid: 0x0000ffffffffffffctr: 0x0000000000ffffffheader: daffffffffffffffffff

kid: 0x0000ffffffffffffctr: 0x0000000001000000header: dbffffffffffff01000000

kid: 0x0000ffffffffffffctr: 0x00000000ffffffffheader: dbffffffffffffffffffff

kid: 0x0000ffffffffffffctr: 0x0000000100000000header: dcffffffffffff0100000000

kid: 0x0000ffffffffffffctr: 0x000000ffffffffffheader: dcffffffffffffffffffffff

kid: 0x0000ffffffffffffctr: 0x0000010000000000header: ddffffffffffff010000000000

kid: 0x0000ffffffffffffctr: 0x0000ffffffffffffheader: ddffffffffffffffffffffffff

kid: 0x0000ffffffffffffctr: 0x0001000000000000header: deffffffffffff01000000000000

kid: 0x0000ffffffffffffctr: 0x00ffffffffffffffheader: deffffffffffffffffffffffffff

kid: 0x0000ffffffffffffctr: 0x0100000000000000header: dfffffffffffff0100000000000000

kid: 0x0000ffffffffffffctr: 0xffffffffffffffffheader: dfffffffffffffffffffffffffffff

kid: 0x0001000000000000ctr: 0x0000000000000000header: e001000000000000

kid: 0x0001000000000000ctr: 0x0000000000000001header: e101000000000000

kid: 0x0001000000000000ctr: 0x00000000000000ffheader: e801000000000000ff

kid: 0x0001000000000000ctr: 0x0000000000000100header: e9010000000000000100

kid: 0x0001000000000000ctr: 0x000000000000ffffheader: e901000000000000ffff

kid: 0x0001000000000000ctr: 0x0000000000010000header: ea01000000000000010000

kid: 0x0001000000000000ctr: 0x0000000000ffffffheader: ea01000000000000ffffff

kid: 0x0001000000000000ctr: 0x0000000001000000header: eb0100000000000001000000

kid: 0x0001000000000000ctr: 0x00000000ffffffffheader: eb01000000000000ffffffff

kid: 0x0001000000000000ctr: 0x0000000100000000header: ec010000000000000100000000

kid: 0x0001000000000000ctr: 0x000000ffffffffffheader: ec01000000000000ffffffffff

kid: 0x0001000000000000ctr: 0x0000010000000000header: ed01000000000000010000000000

kid: 0x0001000000000000ctr: 0x0000ffffffffffffheader: ed01000000000000ffffffffffff

kid: 0x0001000000000000ctr: 0x0001000000000000header: ee0100000000000001000000000000

kid: 0x0001000000000000ctr: 0x00ffffffffffffffheader: ee01000000000000ffffffffffffff

kid: 0x0001000000000000ctr: 0x0100000000000000header: ef010000000000000100000000000000

kid: 0x0001000000000000ctr: 0xffffffffffffffffheader: ef01000000000000ffffffffffffffff

kid: 0x00ffffffffffffffctr: 0x0000000000000000header: e0ffffffffffffff

kid: 0x00ffffffffffffffctr: 0x0000000000000001header: e1ffffffffffffff

kid: 0x00ffffffffffffffctr: 0x00000000000000ffheader: e8ffffffffffffffff

kid: 0x00ffffffffffffffctr: 0x0000000000000100header: e9ffffffffffffff0100

kid: 0x00ffffffffffffffctr: 0x000000000000ffffheader: e9ffffffffffffffffff

kid: 0x00ffffffffffffffctr: 0x0000000000010000header: eaffffffffffffff010000

kid: 0x00ffffffffffffffctr: 0x0000000000ffffffheader: eaffffffffffffffffffff

kid: 0x00ffffffffffffffctr: 0x0000000001000000header: ebffffffffffffff01000000

kid: 0x00ffffffffffffffctr: 0x00000000ffffffffheader: ebffffffffffffffffffffff

kid: 0x00ffffffffffffffctr: 0x0000000100000000header: ecffffffffffffff0100000000

kid: 0x00ffffffffffffffctr: 0x000000ffffffffffheader: ecffffffffffffffffffffffff

kid: 0x00ffffffffffffffctr: 0x0000010000000000header: edffffffffffffff010000000000

kid: 0x00ffffffffffffffctr: 0x0000ffffffffffffheader: edffffffffffffffffffffffffff

kid: 0x00ffffffffffffffctr: 0x0001000000000000header: eeffffffffffffff01000000000000

kid: 0x00ffffffffffffffctr: 0x00ffffffffffffffheader: eeffffffffffffffffffffffffffff

kid: 0x00ffffffffffffffctr: 0x0100000000000000header: efffffffffffffff0100000000000000

kid: 0x00ffffffffffffffctr: 0xffffffffffffffffheader: efffffffffffffffffffffffffffffff

kid: 0x0100000000000000ctr: 0x0000000000000000header: f00100000000000000

kid: 0x0100000000000000ctr: 0x0000000000000001header: f10100000000000000

kid: 0x0100000000000000ctr: 0x00000000000000ffheader: f80100000000000000ff

kid: 0x0100000000000000ctr: 0x0000000000000100header: f901000000000000000100

kid: 0x0100000000000000ctr: 0x000000000000ffffheader: f90100000000000000ffff

kid: 0x0100000000000000ctr: 0x0000000000010000header: fa0100000000000000010000

kid: 0x0100000000000000ctr: 0x0000000000ffffffheader: fa0100000000000000ffffff

kid: 0x0100000000000000ctr: 0x0000000001000000header: fb010000000000000001000000

kid: 0x0100000000000000ctr: 0x00000000ffffffffheader: fb0100000000000000ffffffff

kid: 0x0100000000000000ctr: 0x0000000100000000header: fc01000000000000000100000000

kid: 0x0100000000000000ctr: 0x000000ffffffffffheader: fc0100000000000000ffffffffff

kid: 0x0100000000000000ctr: 0x0000010000000000header: fd0100000000000000010000000000

kid: 0x0100000000000000ctr: 0x0000ffffffffffffheader: fd0100000000000000ffffffffffff

kid: 0x0100000000000000ctr: 0x0001000000000000header: fe010000000000000001000000000000

kid: 0x0100000000000000ctr: 0x00ffffffffffffffheader: fe0100000000000000ffffffffffffff

kid: 0x0100000000000000ctr: 0x0100000000000000header: ff010000000000000001000000000000        00

kid: 0x0100000000000000ctr: 0xffffffffffffffffheader: ff0100000000000000ffffffffffffff        ff

kid: 0xffffffffffffffffctr: 0x0000000000000000header: f0ffffffffffffffff

kid: 0xffffffffffffffffctr: 0x0000000000000001header: f1ffffffffffffffff

kid: 0xffffffffffffffffctr: 0x00000000000000ffheader: f8ffffffffffffffffff

kid: 0xffffffffffffffffctr: 0x0000000000000100header: f9ffffffffffffffff0100

kid: 0xffffffffffffffffctr: 0x000000000000ffffheader: f9ffffffffffffffffffff

kid: 0xffffffffffffffffctr: 0x0000000000010000header: faffffffffffffffff010000

kid: 0xffffffffffffffffctr: 0x0000000000ffffffheader: faffffffffffffffffffffff

kid: 0xffffffffffffffffctr: 0x0000000001000000header: fbffffffffffffffff01000000

kid: 0xffffffffffffffffctr: 0x00000000ffffffffheader: fbffffffffffffffffffffffff

kid: 0xffffffffffffffffctr: 0x0000000100000000header: fcffffffffffffffff0100000000

kid: 0xffffffffffffffffctr: 0x000000ffffffffffheader: fcffffffffffffffffffffffffff

kid: 0xffffffffffffffffctr: 0x0000010000000000header: fdffffffffffffffff010000000000

kid: 0xffffffffffffffffctr: 0x0000ffffffffffffheader: fdffffffffffffffffffffffffffff

kid: 0xffffffffffffffffctr: 0x0001000000000000header: feffffffffffffffff01000000000000

kid: 0xffffffffffffffffctr: 0x00ffffffffffffffheader: feffffffffffffffffffffffffffffff

kid: 0xffffffffffffffffctr: 0x0100000000000000header: ffffffffffffffffff01000000000000        00

kid: 0xffffffffffffffffctr: 0xffffffffffffffffheader: ffffffffffffffffffffffffffffffff        ff

C.2.AEAD Encryption/Decryption Using AES-CTR and HMAC

For each case, we provide:¶

• cipher_suite: The index of the cipher suite in use (seeSection 8.1)¶

• key: Thekey input to encryption/decryption¶

• enc_key: The encryption subkey produced by thederive_subkeys() algorithm¶

• auth_key: The encryption subkey produced by thederive_subkeys() algorithm¶

• nonce: Thenonce input to encryption/decryption¶

• aad: Theaad input to encryption/decryption¶

• pt: The plaintext¶

• ct: The ciphertext¶

An implementation should verify that the following are true, whereAEAD.Encrypt andAEAD.Decrypt are as defined inSection 4.5.1:¶

• AEAD.Encrypt(key, nonce, aad, pt) == ct¶

• AEAD.Decrypt(key, nonce, aad, ct) == pt¶

The other values in the test vector are intermediate values provided tofacilitate debugging of test failures.¶

cipher_suite: 0x0001key: 000102030405060708090a0b0c0d0e0f     101112131415161718191a1b1c1d1e1f     202122232425262728292a2b2c2d2e2fenc_key: 000102030405060708090a0b0c0d0e0fauth_key: 101112131415161718191a1b1c1d1e1f          202122232425262728292a2b2c2d2e2fnonce: 101112131415161718191a1baad: 4945544620534672616d65205747pt: 64726166742d696574662d736672616d    652d656e63ct: 6339af04ada1d064688a442b8dc69d5b    6bfa40f4bef0583e8081069cc60705

cipher_suite: 0x0002key: 000102030405060708090a0b0c0d0e0f     101112131415161718191a1b1c1d1e1f     202122232425262728292a2b2c2d2e2fenc_key: 000102030405060708090a0b0c0d0e0fauth_key: 101112131415161718191a1b1c1d1e1f          202122232425262728292a2b2c2d2e2fnonce: 101112131415161718191a1baad: 4945544620534672616d65205747pt: 64726166742d696574662d736672616d    652d656e63ct: 6339af04ada1d064688a442b8dc69d5b    6bfa40f4be6e93b7da076927bb

cipher_suite: 0x0003key: 000102030405060708090a0b0c0d0e0f     101112131415161718191a1b1c1d1e1f     202122232425262728292a2b2c2d2e2fenc_key: 000102030405060708090a0b0c0d0e0fauth_key: 101112131415161718191a1b1c1d1e1f          202122232425262728292a2b2c2d2e2fnonce: 101112131415161718191a1baad: 4945544620534672616d65205747pt: 64726166742d696574662d736672616d    652d656e63ct: 6339af04ada1d064688a442b8dc69d5b    6bfa40f4be09480509

C.3.SFrame Encryption/Decryption

For each case, we provide:¶

• cipher_suite: The index of the cipher suite in use (seeSection 8.1)¶

• kid: A KID value¶

• ctr: A CTR value¶

• base_key: Thebase_key input to thederive_key_salt algorithm¶

• sframe_key_label: The label used to derivesframe_key in thederive_key_salt algorithm¶

• sframe_salt_label: The label used to derivesframe_salt in thederive_key_salt algorithm¶

• sframe_secret: Thesframe_secret variable in thederive_key_salt algorithm¶

• sframe_key: Thesframe_key value produced by thederive_key_salt algorithm¶

• sframe_salt: Thesframe_salt value produced by thederive_key_salt algorithm¶

• metadata: Themetadata input to the SFrameencrypt algorithm¶

• pt: The plaintext¶

• ct: The SFrame ciphertext¶

An implementation should verify that the following are true, whereencrypt anddecrypt are as defined inSection 4.4, using an SFramecontext initialized withbase_key assigned tokid:¶

• encrypt(ctr, kid, metadata, plaintext) == ct¶

• decrypt(metadata, ct) == pt¶

The other values in the test vector are intermediate values provided tofacilitate debugging of test failures.¶

cipher_suite: 0x0001kid: 0x0000000000000123ctr: 0x0000000000004567base_key: 000102030405060708090a0b0c0d0e0fsframe_key_label: 534672616d6520312e30205365637265                  74206b65792000000000000001230001sframe_salt_label: 534672616d6520312e30205365637265                   742073616c7420000000000000012300                   01sframe_secret: d926952ca8b7ec4a95941d1ada3a5203               ceff8cceee34f574d23909eb314c40c0sframe_key: 3f7d9a7c83ae8e1c8a11ae695ab59314            b367e359fadac7b9c46b2bc6f81f46e1            6b96f0811868d59402b7e870102720b3sframe_salt: 50b29329a04dc0f184ac3168metadata: 4945544620534672616d65205747nonce: 50b29329a04dc0f184ac740faad: 99012345674945544620534672616d65     205747pt: 64726166742d696574662d736672616d    652d656e63ct: 9901234567449408b6f490086165b9d6    f62b24ae1a59a56486b4ae8ed036b889    12e24f11

cipher_suite: 0x0002kid: 0x0000000000000123ctr: 0x0000000000004567base_key: 000102030405060708090a0b0c0d0e0fsframe_key_label: 534672616d6520312e30205365637265                  74206b65792000000000000001230002sframe_salt_label: 534672616d6520312e30205365637265                   742073616c7420000000000000012300                   02sframe_secret: d926952ca8b7ec4a95941d1ada3a5203               ceff8cceee34f574d23909eb314c40c0sframe_key: e2ec5c797540310483b16bf6e7a570d2            a27d192fe869c7ccd8584a8d9dab9154            9fbe553f5113461ec6aa83bf3865553esframe_salt: e68ac8dd3d02fbcd368c5577metadata: 4945544620534672616d65205747nonce: e68ac8dd3d02fbcd368c1010aad: 99012345674945544620534672616d65     205747pt: 64726166742d696574662d736672616d    652d656e63ct: 99012345673f31438db4d09434e43afa    0f8a2f00867a2be085046a9f5cb4f101    d607

cipher_suite: 0x0003kid: 0x0000000000000123ctr: 0x0000000000004567base_key: 000102030405060708090a0b0c0d0e0fsframe_key_label: 534672616d6520312e30205365637265                  74206b65792000000000000001230003sframe_salt_label: 534672616d6520312e30205365637265                   742073616c7420000000000000012300                   03sframe_secret: d926952ca8b7ec4a95941d1ada3a5203               ceff8cceee34f574d23909eb314c40c0sframe_key: 2c5703089cbb8c583475e4fc461d97d1            8809df79b6d550f78eb6d50ffa80d892            11d57909934f46f5405e38cd583c69fesframe_salt: 38c16e4f5159700c00c7f350metadata: 4945544620534672616d65205747nonce: 38c16e4f5159700c00c7b637aad: 99012345674945544620534672616d65     205747pt: 64726166742d696574662d736672616d    652d656e63ct: 990123456717fc8af28a5a695afcfc6c    8df6358a17e26b2fcb3bae32e443

cipher_suite: 0x0004kid: 0x0000000000000123ctr: 0x0000000000004567base_key: 000102030405060708090a0b0c0d0e0fsframe_key_label: 534672616d6520312e30205365637265                  74206b65792000000000000001230004sframe_salt_label: 534672616d6520312e30205365637265                   742073616c7420000000000000012300                   04sframe_secret: d926952ca8b7ec4a95941d1ada3a5203               ceff8cceee34f574d23909eb314c40c0sframe_key: d34f547f4ca4f9a7447006fe7fcbf768sframe_salt: 75234edefe07819026751816metadata: 4945544620534672616d65205747nonce: 75234edefe07819026755d71aad: 99012345674945544620534672616d65     205747pt: 64726166742d696574662d736672616d    652d656e63ct: 9901234567b7412c2513a1b66dbb4884    1bbaf17f598751176ad847681a69c6d0    b091c07018ce4adb34eb

cipher_suite: 0x0005kid: 0x0000000000000123ctr: 0x0000000000004567base_key: 000102030405060708090a0b0c0d0e0fsframe_key_label: 534672616d6520312e30205365637265                  74206b65792000000000000001230005sframe_salt_label: 534672616d6520312e30205365637265                   742073616c7420000000000000012300                   05sframe_secret: 0fc3ea6de6aac97a35f194cf9bed94d4               b5230f1cb45a785c9fe5dce9c188938a               b6ba005bc4c0a19181599e9d1bcf7b74               aca48b60bf5e254e546d809313e083a3sframe_key: d3e27b0d4a5ae9e55df01a70e6d4d28d            969b246e2936f4b7a5d9b494da6b9633sframe_salt: 84991c167b8cd23c93708ec7metadata: 4945544620534672616d65205747nonce: 84991c167b8cd23c9370cba0aad: 99012345674945544620534672616d65     205747pt: 64726166742d696574662d736672616d    652d656e63ct: 990123456794f509d36e9beacb0e261d    99c7d1e972f1fed787d4049f17ca2135    3c1cc24d56ceabced279