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Network Working Group                                    D. Eastlake 3rdRequest for Comments: 3797                         Motorola LaboratoriesObsoletes:2777                                                June 2004Category: InformationalPublicly Verifiable Nominations Committee (NomCom) Random SelectionStatus of this Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2004).Abstract   This document describes a method for making random selections in such   a way that the unbiased nature of the choice is publicly verifiable.   As an example, the selection of the voting members of the IETF   Nominations Committee (NomCom) from the pool of eligible volunteers   is used.  Similar techniques would be applicable to other cases.Table of Contents1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . .22. General Flow of a Publicly Verifiable Process . . . . . . . . .22.1.  Determination of the Pool . . . . . . . . . . . . . . . .22.2.  Publication of the Algorithm. . . . . . . . . . . . . . .32.3.  Publication of Selection. . . . . . . . . . . . . . . . .33. Randomness. . . . . . . . . . . . . . . . . . . . . . . . . . .33.1.  Sources of Randomness . . . . . . . . . . . . . . . . . .33.2.  Skew. . . . . . . . . . . . . . . . . . . . . . . . . . .43.3.  Entropy Needed. . . . . . . . . . . . . . . . . . . . . .44. A Suggested Precise Algorithm . . . . . . . . . . . . . . . . .55. Handling Real World Problems. . . . . . . . . . . . . . . . . .75.1.  Uncertainty as to the Pool. . . . . . . . . . . . . . . .75.2.  Randomness Ambiguities. . . . . . . . . . . . . . . . . .76. Fully Worked Example. . . . . . . . . . . . . . . . . . . . . .87. Security Considerations . . . . . . . . . . . . . . . . . . . .98. Reference Code. . . . . . . . . . . . . . . . . . . . . . . . .10Appendix A: History of NomCom Member Selection . . . . . . . . . .16Appendix B: Changes fromRFC 2777. . . . . . . . . . . . . . . . .16   Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . .17Eastlake 3rd                 Informational                      [Page 1]

RFC 3797              Verifiable Random Selection              June 2004   References . . . . . . . . . . . . . . . . . . . . . . . . . . . .17      Normative References. . . . . . . . . . . . . . . . . . . . . .17      Informative References. . . . . . . . . . . . . . . . . . . . .17   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . .18   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . .191.  Introduction   Under the IETF rules, each year ten people are randomly selected from   among eligible volunteers to be the voting members of the IETF   nominations committee (NomCom).  The NomCom nominates members of the   Internet Engineering Steering Group (IESG) and the Internet   Architecture Board (IAB) as described in [RFC 3777].  The number of   eligible volunteers in recent years has been around 100.   It is highly desirable that the random selection of the voting NomCom   be done in an unimpeachable fashion so that no reasonable charges of   bias or favoritism can be brought.  This is as much for the   protection of the selection administrator (currently, the appointed   non-voting NomCom chair) from suspicion of bias as it is for the   protection of the IETF.   A method such that public information will enable any person to   verify the randomness of the selection meets this criterion.  This   document gives an example of such a method.   The method, in the form it appears inRFC 2777, was also used by IANA   in February 2003 to determine the ACE prefix for Internationalized   Domain Names [RFC 3490] so as to avoid claim jumping.2.  General Flow of a Publicly Verifiable Process   A selection of NomCom members publicly verifiable as unbiased or   similar selection could follow the three steps given below.2.1.  Determination of the Pool   First, determine the pool from which the selection is to be made as   provided in [RFC 3777] or its successor.   Volunteers are solicited by the selection administrator.  Their names   are then passed through the IETF Secretariat to check eligibility.   (Current eligibility criteria relate to IETF meeting attendance,   records of which are maintained by the Secretariat.)  The full list   of eligible volunteers is made public early enough that a reasonable   time can be given to resolve any disputes as to who should be in the   pool.Eastlake 3rd                 Informational                      [Page 2]

RFC 3797              Verifiable Random Selection              June 20042.2.  Publication of the Algorithm   The exact algorithm to be used, including the public future sources   of randomness, is made public.  For example, the members of the final   list of eligible volunteers are ordered by publicly numbering them,   some public future sources of randomness such as government run   lotteries are specified, and an exact algorithm is specified whereby   eligible volunteers are selected based on a strong hash function   [RFC 1750] of these future sources of randomness.2.3.  Publication of Selection   When the pre-specified sources of randomness produce their output,   those values plus a summary of the execution of the algorithm for   selection should be announced so that anyone can verify that the   correct randomness source values were used and the algorithm properly   executed.  The algorithm can be run to select, in an ordered fashion,   a larger number than are actually necessary so that if any of those   selected need to be passed over or replaced for any reason, an   ordered set of additional alternate selections will be available.  A   cut off time for any complaint that the algorithm was run with the   wrong inputs or not faithfully executed must be specified to finalize   the output and provide a stable selection.3.  Randomness   The crux of the unbiased nature of the selection is that it is based   in an exact, predetermined fashion on random information which will   be revealed in the future and thus can not be known to the person   specifying the algorithm.  That random information will be used to   control the selection.  The random information must be such that it   will be publicly and unambiguously revealed in a timely fashion.   The random sources must not include anything that any reasonable   person would believe to be under the control or influence of the IETF   or its components, such as IETF meeting attendance statistics,   numbers of documents issued, or the like.3.1.  Sources of Randomness   Examples of good information to use are winning lottery numbers for   specified runnings of specified public lotteries.  Particularly for   government run lotteries, great care is taken to see that they occur   on time and produce random quantities.  Even in the unlikely case one   were to have been rigged, it would almost certainly be in connection   with winning money in the lottery, not in connection with IETF use.Eastlake 3rd                 Informational                      [Page 3]

RFC 3797              Verifiable Random Selection              June 2004   Other possibilities are such things as the daily balance in the US   Treasury on a specified day, the volume of trading on the New York   Stock exchange on a specified day, etc.  (However, the reference code   given below will not handle integers that are too large.)  Sporting   events can also be used.  (Experience has indicated that stock prices   and/or volumes are a poor source of unambiguous data due trading   suspensions, company mergers, delistings, splits, multiple markets,   etc.)  In all cases, great care must be taken to specify exactly what   quantities are being presumed random and what will be done if their   issuance is cancelled, delayed, or advanced.   It is important that the last source of randomness, chronologically,   produce a substantial amount of the entropy needed.  If most of the   randomness has come from the earlier of the specified sources, and   someone has even limited influence on the final source, they might do   an exhaustive analysis and exert such influence so as to bias the   selection in the direction they wanted.  Thus it is best for the last   source to be an especially strong and unbiased source of a large   amount of randomness such as a government run lottery.   It is best not to use too many different sources.  Every additional   source increases the probability that one or more sources might be   delayed, cancelled, or just plain screwed up somehow, calling into   play contingency provisions or, worst of all, creating a situation   that was not anticipated.  This would either require arbitrary   judgment by the selection administrator, defeating the randomness of   the selection, or a re-run with a new set of sources, causing much   delay.  Three or four would be a good number of sources.  Ten is too   many.3.2.  Skew   Some of the sources of randomness produce data that is not uniformly   distributed.  This is certainly true of volumes, prices, and horse   race results, for example.  However, use of a strong mixing function   [RFC 1750] will extract the available entropy and produce a hash   value whose bits, remainder modulo a small divisor, etc., deviate   from a uniform distribution only by an insignificant amount.3.3.  Entropy Needed   What we are doing is selecting N items without replacement from a   population of P items.  The number of different ways to do this is as   follows, where "!" represents the factorial function:                            P!                       -------------                       N! * (P - N)!Eastlake 3rd                 Informational                      [Page 4]

RFC 3797              Verifiable Random Selection              June 2004   To do this in a completely random fashion requires as many random   bits as the logarithm base 2 of that quantity.  Some sample   calculated approximate number of random bits for the completely   random selection of 10 NomCom members from various pool sizes is   given below:               Random Selection of Ten Items From Pool     Pool size     20   25   30   35   40   50   60   75  100  120     Bits needed   18   22   25   28   30   34   37   40   44   47   Using an inadequate number of bits means that not all of the possible   sets of ten selected items would be available.  For a substantially   inadequate amount of entropy, there could be a significant   correlation between the selection of two different members of the   pool, for example.  However, as a practical matter, for pool sizes   likely to be encountered in IETF NomCom membership selection, 40 bits   of entropy should always be adequate.  Even if there is a large pool   and more bits are needed for perfect randomness, 40 bits of entropy   will assure only an insignificant deviation from completely random   selection for the difference in probability of selection of different   pool members, the correlation between the selection of any pair of   pool members, etc.   An MD5 [RFC 1321] hash has 128 bits and therefore can produce no more   than that number of bits of entropy.  However, this is more than   three times what is likely to ever be needed for IETF NomCom   membership selection.  A even stronger hash, such as SHA-1   [RFC 3174], can be used if desired.4.  A Suggested Precise Algorithm   It is important that a precise algorithm be given for mixing the   random sources specified and making the selection based thereon.   Sources suggested above produce either a single positive number   (i.e., NY Stock Exchange volume in thousands of shares) or a small   set of positive numbers (many lotteries provide 6 numbers in the   range of 1 through 40 or the like, a sporting event could produce the   scores of two teams, etc.).  A suggested precise algorithm is as   follows:      1. For each source producing multiple numeric values, represent         each as a decimal number terminated by a period (or with a         period separating the whole from the fractional part), without         leading zeroes (except for a single leading zero if the integer         part is zero), and without trailing zeroes after the period.Eastlake 3rd                 Informational                      [Page 5]

RFC 3797              Verifiable Random Selection              June 2004      2. Order the values from each source from smallest to the largest         and concatenate them and suffix the result with a "/".  For         each source producing a single number, simply represent it as         above with a suffix "/".  (This sorting is necessary because         the same lottery results, for example, are sometimes reported         in the order numbers were drawn and sometimes in numeric order         and such things as the scores of two sports teams that play a         game has no inherent order.)      3. At this point you have a string for each source, say s1/, s2/,         ...  Concatenate these strings in a pre-specified order, the         order in which the sources were listed if not otherwise         specified, and represent each character as its ASCII code         [ASCII] producing "s1/s2/.../".   You then produce a sequence of random values derived from a strong   mixing of these sources by calculating the MD5 hash [RFC 1321] of   this string prefixed and suffixed with an all zeros two byte sequence   for the first value, the string prefixed and suffixed by 0x0001 for   the second value, etc., treating the two bytes as a big endian   counter.  Treat each of these derived "random" MD5 output values as a   positive 128-bit multiprecision big endian integer.   Then totally order the pool of listed volunteers as follows: If there   are P volunteers, select the first by dividing the first derived   random value by P and using the remainder plus one as the position of   the selectee in the published list.  Select the second by dividing   the second derived random value by P-1 and using the remainder plus   one as the position in the list with the first selected person   eliminated.  Etc.   It is STRONGLY recommended that alphanumeric random sources be   avoided due to the much greater difficulty in canonicalizing them in   an independently repeatable fashion; however, if you choose to ignore   this advice and use an ASCII or similar Roman alphabet source or   sources, all white space, punctuation, accents, and special   characters should be removed and all letters set to upper case.  This   will leave only an unbroken sequence of letters A-Z and digits 0-9   which can be treated as a canonicalized number above and suffixed   with a "./".  If you choose to not just ignore but flagrantly flout   this advice and try to use even more complex and harder to   canonicalize internationalized text, such as UNICODE, you are on your   own.Eastlake 3rd                 Informational                      [Page 6]

RFC 3797              Verifiable Random Selection              June 20045.  Handling Real World Problems   In the real world, problems can arise in following the steps and flow   outlined in Sections2 through4 above.  Some problems that have   actually arisen are described below with recommendations for handling   them.5.1.  Uncertainty as to the Pool   Every reasonable effort should be made to see that the published pool   from which selection is made is of certain and eligible persons.   However, especially with compressed schedules or perhaps someone   whose claim that they volunteered and are eligible has not been   resolved by the deadline, or a determination that someone is not   eligible which occurs after the publication of the pool, it may be   that there are still uncertainties.   The best way to handle this is to maintain the announced schedule,   INCLUDE in the published pool all those whose eligibility is   uncertain and to keep the published pool list numbering IMMUTABLE   after its publication.  If someone in the pool is later selected by   the algorithm and random input but it has been determined they are   ineligible, they can be skipped and the algorithm run further to make   an additional selection.  Thus the uncertainty only effects one   selection and in general no more than a maximum of U selections where   there are U uncertain pool members.   Other courses of action are far worse.  Actual insertion or deletion   of entries in the pool after its publication changes the length of   the list and totally scrambles who is selected, possibly changing   every selection.  Insertion into the pool raises questions of where   to insert: at the beginning, end, alphabetic order, ... Any such   choices by the selection administrator after the random numbers are   known destroys the public verifiability of fair choice.  Even if done   before the random numbers are known, such dinking with the list after   its publication just smells bad.  There should be clear fixed public   deadlines and someone who challenges their absence from the pool   after the published deadline should have their challenge   automatically denied for tardiness.5.2.  Randomness Ambiguities   The best good faith efforts have been made to specify precise and   unambiguous sources of randomness.  These sources have been made   public in advance and there has not been objection to them.  However,   it has happened that when the time comes to actually get and use this   randomness, the real world has thrown a curve ball and it isn't quite   clear what data to use.  Problems have particularly arisen inEastlake 3rd                 Informational                      [Page 7]

RFC 3797              Verifiable Random Selection              June 2004   connection with stock prices, volumes, and financial exchange rates   or indices.  If volumes that were published in thousands are   published in hundreds, you have a rounding problem.  Prices that were   quoted in fractions or decimals can change to the other.  If you take   care of every contingency that has come up in the past, you can be   hit with a new one.  When this sort of thing happens, it is generally   too late to announce new sources, an action which could raise   suspicions of its own.  About the only course of action is to make a   reasonable choice within the ambiguity and depend on confidence in   the good faith of the selection administrator.  With care, such cases   should be extremely rare.   Based on these experiences, it is again recommended that public   lottery numbers or the like be used as the random inputs and stock   prices and volumes avoided.6.  Fully Worked Example   Assume the following ordered list of 25 eligible volunteers is   published in advance of selection:         1. John         11. Pollyanna       21. Pride         2. Mary         12. Pendragon       22. Sloth         3. Bashful      13. Pandora         23. Envy         4. Dopey        14. Faith           24. Anger         5. Sleepy       15. Hope            25. Kasczynski         6. Grouchy      16. Charity         7. Doc          17. Lee         8. Sneazy       18. Longsuffering         9. Handsome     19. Chastity        10. Cassandra    20. Smith   Assume the following (fake example) ordered list of randomness   sources:   1. The Kingdom of Alphaland State Lottery daily number for 1 November      2004 treated as a single four digit integer.   2. Numbers of the winning horses at Hialeia for all races for the      first day on or after 13 October 2004 on which at least two races      are run.   3. The People's Democratic Republic of Betastani State Lottery six      winning numbers (ignoring the seventh "extra" number) for 1      November 2004.   Hypothetical randomness publicly produced:       Source 1:  9319       Source 2:  2, 5, 12, 8, 10       Source 3:  9, 18, 26, 34, 41, 45Eastlake 3rd                 Informational                      [Page 8]

RFC 3797              Verifiable Random Selection              June 2004   Resulting key string:       9319./2.5.8.10.12./9.18.26.34.41.45./   The table below gives the hex of the MD5 of the above key string   bracketed with a two byte string that is successively 0x0000, 0x0001,   0x0002, through 0x0010 (16 decimal).  The divisor for the number size   of the remaining pool at each stage is given and the index of the   selectee as per the original number of those in the pool.   index        hex value of MD5        div  selected    1  990DD0A5692A029A98B5E01AA28F3459  25  -> 17 <-    2  3691E55CB63FCC37914430B2F70B5EC6  24  ->  7 <-    3  FE814EDF564C190AC1D25753979990FA  23  ->  2 <-    4  1863CCACEB568C31D7DDBDF1D4E91387  22  -> 16 <-    5  F4AB33DF4889F0AF29C513905BE1D758  21  -> 25 <-    6  13EAEB529F61ACFB9A29D0BA3A60DE4A  20  -> 23 <-    7  992DB77C382CA2BDB9727001F3CDCCD9  19  ->  8 <-    8  63AB4258ECA922976811C7F55C383CE7  18  -> 24 <-    9  DFBC5AC97CED01B3A6E348E3CC63F40D  17  -> 19 <-   10  31CB111C4A4EBE9287CEAE16FE51B909  16  -> 13 <-   11  07FA46C122F164C215BBC72793B189A3  15  -> 22 <-   12  AC52F8D75CCBE2E61AFEB3387637D501  14  ->  5 <-   13  53306F73E14FC0B2FBF434218D25948E  13  -> 18 <-   14  B5D1403501A81F9A47318BE7893B347C  12  ->  9 <-   15  85B10B356AA06663EF1B1B407765100A  11  ->  1 <-   16  3269E6CE559ABD57E2BA6AAB495EB9BD  10  ->  4 <-   Resulting first ten selected, in order selected:         1. Lee (17)           6. Envy (23)         2. Doc (7)            7. Sneazy (8)         3. Mary (2)           8. Anger (24)         4. Charity (16)       9. Chastity (19)         5. Kasczynski (25)   10. Pandora (13)   Should one of the above turn out to be ineligible or decline to   serve, the next would be Sloth, number 22.7. Security Considerations   Careful choice of should be made of randomness inputs so that there   is no reasonable suspicion that they are under the control of the   administrator.  Guidelines given above to use a small number of   inputs with a substantial amount of entropy from the last should be   followed.  And equal care needs to be given that the algorithm   selected is faithfully executed with the designated inputs values.Eastlake 3rd                 Informational                      [Page 9]

RFC 3797              Verifiable Random Selection              June 2004   Publication of the results and a week or so window for the community   of interest to duplicate the calculations should give a reasonable   assurance against implementation tampering.8.  Reference Code   This code makes use of the MD5 reference code from [RFC 1321] ("RSA   Data Security, Inc.  MD5 Message-Digest Algorithm").  The portion of   the code dealing with multiple floating point numbers was written by   Matt Crawford.  The original code inRFC 2777 could only handle pools   of up to 255 members and was extended to 2**16-1 by Erik Nordmark.   This code has been extracted from this document, compiled, and   tested.  While no flaws have been found, it is possible that when   used with some compiler on some system some flaw will manifest   itself.   /****************************************************************     *     *  Reference code for     *      "Publicly Verifiable Random Selection"     *          Donald E. Eastlake 3rd     *              February 2004     *     ****************************************************************/    #include <limits.h>    #include <math.h>    #include <stdio.h>    #include <stdlib.h>    #include <string.h>    /* FromRFC 1321 */    #include "global.h"    #include "MD5.h"    /* local prototypes */    int longremainder ( unsigned short divisor,                        unsigned char dividend[16] );    long int getinteger ( char *string );    double NPentropy ( int N, int P );    /* limited to up to 16 inputs of up to sixteen integers each */    /* pool limit of 2**8-1 extended to 2**16-1 by Erik Nordmark */    /****************************************************************/    main ()    {    int         i, j,  k, k2, err, keysize, selection, usel;Eastlake 3rd                 Informational                     [Page 10]

RFC 3797              Verifiable Random Selection              June 2004    unsigned short   remaining, *selected;    long int    pool, temp, array[16];    MD5_CTX     ctx;    char        buffer[257], key [800], sarray[16][256];    unsigned char    uc16[16], unch1, unch2;    pool = getinteger ( "Type size of pool:\n" );    if ( pool > 65535 )        {        printf ( "Pool too big.\n" );        exit ( 1 );        }    selected = (unsigned short *) malloc ( (size_t)pool );    if ( !selected )        {        printf ( "Out of memory.\n" );        exit ( 1 );        }    selection = getinteger ( "Type number of items to be selected:\n" );    if ( selection > pool )        {        printf ( "Pool too small.\n" );        exit ( 1 );        }    if ( selection == pool )        printf ( "All of the pool is selected.\n" );    else        {        err = printf ( "Approximately %.1f bits of entropy needed.\n",                        NPentropy ( selection, pool ) + 0.1 );        if ( err <= 0 ) exit ( 1 );        }    for ( i = 0, keysize = 0; i < 16; ++i )        {        if ( keysize > 500 )            {            printf ( "Too much input.\n" );            exit ( 1 );            }        /* get the "random" inputs. echo back to user so the user may           be able to tell if truncation or other glitches occur.  */        err = printf (            "\nType #%d randomness or 'end' followed by new line.\n"            "Up to 16 integers or the word 'float' followed by up\n"            "to 16 x.y format reals.\n", i+1 );        if ( err <= 0 ) exit ( 1 );        gets ( buffer );Eastlake 3rd                 Informational                     [Page 11]

RFC 3797              Verifiable Random Selection              June 2004        j = sscanf ( buffer,                "%ld%ld%ld%ld%ld%ld%ld%ld%ld%ld%ld%ld%ld%ld%ld%ld",            &array[0], &array[1], &array[2], &array[3],            &array[4], &array[5], &array[6], &array[7],            &array[8], &array[9], &array[10], &array[11],            &array[12], &array[13], &array[14], &array[15] );        if ( j == EOF )            exit ( j );        if ( !j )            if ( buffer[0] == 'e' )                break;            else                {   /* floating point code by Matt Crawford */                j = sscanf ( buffer,                    "float %ld.%[0-9]%ld.%[0-9]%ld.%[0-9]%ld.%[0-9]"                    "%ld.%[0-9]%ld.%[0-9]%ld.%[0-9]%ld.%[0-9]"                    "%ld.%[0-9]%ld.%[0-9]%ld.%[0-9]%ld.%[0-9]"                    "%ld.%[0-9]%ld.%[0-9]%ld.%[0-9]%ld.%[0-9]",                    &array[0], sarray[0], &array[1], sarray[1],                    &array[2], sarray[2], &array[3], sarray[3],                    &array[4], sarray[4], &array[5], sarray[5],                    &array[6], sarray[6], &array[7], sarray[7],                    &array[8], sarray[8], &array[9], sarray[9],                    &array[10], sarray[10], &array[11], sarray[11],                    &array[12], sarray[12], &array[13], sarray[13],                    &array[14], sarray[14], &array[15], sarray[15] );                if ( j == 0 || j & 1 )                    printf ( "Bad format." );                else {                     for ( k = 0, j /= 2; k < j; k++ )                     {                           /* strip trailing zeros */                     for ( k2=strlen(sarray[k]); sarray[k][--k2]=='0';)                           sarray[k][k2] = '\0';                     err = printf ( "%ld.%s\n", array[k], sarray[k] );                     if ( err <= 0 ) exit ( 1 );                     keysize += sprintf ( &key[keysize], "%ld.%s",                                          array[k], sarray[k] );                     }                     keysize += sprintf ( &key[keysize], "/" );                     }                }        else            {   /* sort values, not a very efficient algorithm */            for ( k2 = 0; k2 < j - 1; ++k2 )                for ( k = 0; k < j - 1; ++k )                    if ( array[k] > array[k+1] )Eastlake 3rd                 Informational                     [Page 12]

RFC 3797              Verifiable Random Selection              June 2004                        {                        temp = array[k];                        array[k] = array[k+1];                        array[k+1] = temp;                        }            for ( k = 0; k < j; ++k )                { /* print for user check */                err = printf ( "%ld ", array[k] );                if ( err <= 0 ) exit ( 1 );                keysize += sprintf ( &key[keysize], "%ld.", array[k] );                }            keysize += sprintf ( &key[keysize], "/" );            }        }   /* end for i */    /* have obtained all the input, now produce the output */    err = printf ( "Key is:\n %s\n", key );    if ( err <= 0 ) exit ( 1 );    for ( i = 0; i < pool; ++i )        selected [i] = (unsigned short)(i + 1);    printf ( "index        hex value of MD5        div  selected\n" );    for (   usel = 0, remaining = (unsigned short)pool;            usel < selection;            ++usel, --remaining )        {        unch1 = (unsigned char)usel;        unch2 = (unsigned char)(usel>>8);        /* prefix/suffix extended to 2 bytes by Donald Eastlake */        MD5Init ( &ctx );        MD5Update ( &ctx, &unch2, 1 );        MD5Update ( &ctx, &unch1, 1 );        MD5Update ( &ctx, (unsigned char *)key, keysize );        MD5Update ( &ctx, &unch2, 1 );        MD5Update ( &ctx, &unch1, 1 );        MD5Final ( uc16, &ctx );        k = longremainder ( remaining, uc16 );    /* printf ( "Remaining = %d, remainder = %d.\n", remaining, k ); */        for ( j = 0; j < pool; ++j )            if ( selected[j] )                if ( --k < 0 )                    {                    printf ( "%2d  "    "%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X  "    "%2d  -> %2d <-\n",    usel+1, uc16[0],uc16[1],uc16[2],uc16[3],uc16[4],uc16[5],uc16[6],    uc16[7],uc16[8],uc16[9],uc16[10],uc16[11],uc16[12],uc16[13],    uc16[14],uc16[15], remaining, selected[j] );                    selected[j] = 0;Eastlake 3rd                 Informational                     [Page 13]

RFC 3797              Verifiable Random Selection              June 2004                    break;                    }        }     printf ( "\nDone, type any character to exit.\n" );     getchar ();     return 0;     }     /* prompt for a positive non-zero integer input */     /****************************************************************/     long int getinteger ( char *string )     {     long int     i;     int          j;     char    tin[257];     while ( 1 )     {     printf ( string );     printf ( "(or 'exit' to exit) " );     gets ( tin );     j = sscanf ( tin, "%ld", &i );     if (    ( j == EOF )         ||  ( !j && ( ( tin[0] == 'e' ) || ( tin[0] == 'E' ) ) )             )         exit ( j );     if ( ( j == 1 ) &&          ( i > 0 ) )         return i;     }   /* end while */     }     /* get remainder of dividing a 16 byte unsigned int        by a small positive number */     /****************************************************************/     int longremainder ( unsigned short divisor,                         unsigned char dividend[16] )     {     int i;     long int kruft;     if ( !divisor )         return -1;     for ( i = 0, kruft = 0; i < 16; ++i )         {         kruft = ( kruft << 8 ) + dividend[i];         kruft %= divisor;Eastlake 3rd                 Informational                     [Page 14]

RFC 3797              Verifiable Random Selection              June 2004         }     return kruft;     }   /* end longremainder */    /* calculate how many bits of entropy it takes to select N from P */    /****************************************************************/    /*             P!      log  ( ----------------- )         2    N! * ( P - N )!    */    double NPentropy ( int N, int P )    {    int         i;    double      result = 0.0;    if (    ( N < 1 )   /* not selecting anything? */       ||   ( N >= P )  /* selecting all of pool or more? */       )        return 0.0;     /* degenerate case */    for ( i = P; i > ( P - N ); --i )        result += log ( i );    for ( i = N; i > 1; --i )        result -= log ( i );    /* divide by [ log (base e) of 2 ] to convert to bits */    result /= 0.69315;    return result;    }   /* end NPentropy */Eastlake 3rd                 Informational                     [Page 15]

RFC 3797              Verifiable Random Selection              June 2004Appendix A: History of NomCom Member Selection   For reference purposes, here is a list of the IETF Nominations   Committee member selection techniques and chairs so far:           YEAR      CHAIR               SELECTION METHOD        1993/1994  Jeff Case             Clergy        1994/1995  Fred Baker            Clergy        1995/1996  Guy Almes             Clergy        1996/1997  Geoff Huston          Spouse        1997/1998  Mike St.Johns         Algorithm        1998/1999  Donald Eastlake 3rdRFC 2777        1999/2000  Avri DoriaRFC 2777        2000/2001  Bernard AbobaRFC 2777        2001/2002  Theodore Ts'oRFC 2777        2002/2003  Phil RobertsRFC 2777        2003/2004  Rich DravesRFC 2777   Clergy = Names were written on pieces of paper, placed in a   receptacle, and a member of the clergy picked the NomCom members.   Spouse = Same as Clergy except chair's spouse made the selection.   Algorithm = Algorithmic selection based on similar concepts to those   documented inRFC 2777 and herein.RFC 2777 = Algorithmic selection using the algorithm and reference   code provided inRFC 2777 (but not the fake example sources of   randomness).Appendix B: Changes fromRFC 2777   This document differs from [RFC 2777], the previous version, in three   primary ways as follows:   (1)Section 5, on problems actually encountered with using these       recommendations for selecting an IETF NomCom and on how to handle       them, has been added.   (2) The selection algorithm code has been modified to handle pools of       up to 2**16-1 elements and the counter based prefix and suffix       concatenated with the key string before hashing has been extended       to two bytes.   (3) Mention has been added that the algorithm documented herein was       used by IANA to select the Internationalized Domain Name ACE       prefix and some minor wording changes made.Eastlake 3rd                 Informational                     [Page 16]

RFC 3797              Verifiable Random Selection              June 2004   (4) References have been divided into Informative and Normative.   (5) The list inAppendix A has been brought up to date.Acknowledgements   Matt Crawford and Erik Nordmark made major contributions to this   document.  Comments by Bernard Aboba, Theodore Ts'o, Jim Galvin,   Steve Bellovin, and others have been incorporated.ReferencesNormative References   [ASCII]    "USA Standard Code for Information Interchange", X3.4,              American National Standards Institute: New York, 1968.   [RFC 1321] Rivest, R., "The MD5 Message-Digest Algorithm",RFC 1321,              April 1992.   [RFC 1750] Eastlake, 3rd, D., Crocker, S. and J. Schiller,              "Randomness Recommendations for Security",RFC 1750,              December 1994.   [RFC 3174] Eastlake, 3rd, D. and P. Jones, "US Secure Hash Algorithm              1 (SHA1)",RFC 3174, September 2001.Informative References   [RFC 3777] Galvin, J., "IAB and IESG Selection, Confirmation, and              Recall Process: Operation of the Nominating and Recall              Committees",BCP 10,RFC 3777, April 2004.   [RFC 2777] Eastlake, 3rd, D., "Publicly Verifiable Nomcom Random              Selection",RFC 2777, February 2000.   [RFC 3490] Falstrom, P., Hoffman, P. and A. Costello,              "Internationalizing Domain Names in Applications (IDNA)",RFC 3490, March 2003.Eastlake 3rd                 Informational                     [Page 17]

RFC 3797              Verifiable Random Selection              June 2004Author's Address   Donald E. Eastlake, 3rd   Motorola Laboratories   155 Beaver Street   Milford, MA 01757 USA   Phone: +1-508-786-7554(w)          +1-508-634-2066(h)   EMail: Donald.Eastlake@motorola.comEastlake 3rd                 Informational                     [Page 18]

RFC 3797              Verifiable Random Selection              June 2004Full Copyright Statement   Copyright (C) The Internet Society (2004).  This document is subject   to the rights, licenses and restrictions contained inBCP 78, and   except as set forth therein, the authors retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at ietf-   ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Eastlake 3rd                 Informational                     [Page 19]