rand
packagestandard library
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Documentation¶
Overview¶
Package rand implements a cryptographically securerandom number generator.
Index¶
Examples¶
Constants¶
This section is empty.
Variables¶
var Readerio.ReaderReader is a global, shared instance of a cryptographicallysecure random number generator. It is safe for concurrent use.
- On Linux, FreeBSD, Dragonfly, and Solaris, Reader uses getrandom(2).
- On legacy Linux (< 3.17), Reader opens /dev/urandom on first use.
- On macOS, iOS, and OpenBSD Reader, uses arc4random_buf(3).
- On NetBSD, Reader uses the kern.arandom sysctl.
- On Windows, Reader uses the ProcessPrng API.
- On js/wasm, Reader uses the Web Crypto API.
- On wasip1/wasm, Reader uses random_get.
In FIPS 140-3 mode, the output passes through an SP 800-90A Rev. 1Deterministric Random Bit Generator (DRBG).
Functions¶
funcInt¶
Int returns a uniform random value in [0, max). It panics if max <= 0, andreturns an error if rand.Read returns one.
Example¶
ExampleInt prints a single cryptographically secure pseudorandom number between 0 and 99 inclusive.
package mainimport ("crypto/rand""fmt""math/big")func main() {// Int cannot return an error when using rand.Reader.a, _ := rand.Int(rand.Reader, big.NewInt(100))fmt.Println(a.Int64())}funcPrime¶
Prime returns a number of the given bit length that is prime with high probability.Prime will return error for any error returned by rand.Read or if bits < 2.
Example¶
ExamplePrime prints a cryptographically secure pseudorandom 64 bit prime number.
package mainimport ("crypto/rand""fmt")func main() {// Prime cannot return an error when using rand.Reader and bits >= 2.a, _ := rand.Prime(rand.Reader, 64)fmt.Println(a.Int64())}funcRead¶
Read fills b with cryptographically secure random bytes. It never returns anerror, and always fills b entirely.
Read callsio.ReadFull onReader and crashes the program irrecoverably ifan error is returned. The default Reader uses operating system APIs that aredocumented to never return an error on all but legacy Linux systems.
Example¶
ExampleRead prints a cryptographically secure pseudorandom 32 byte key.
package mainimport ("crypto/rand""fmt")func main() {// Note that no error handling is necessary, as Read always succeeds.key := make([]byte, 32)rand.Read(key)// The key can contain any byte value, print the key in hex.fmt.Printf("% x\n", key)}funcText¶added ingo1.24.0
func Text()string
Text returns a cryptographically random string using the standardRFC 4648 base32 alphabetfor use when a secret string, token, password, or other text is needed.The result contains at least 128 bits of randomness, enough to prevent brute forceguessing attacks and to make the likelihood of collisions vanishingly small.A future version may return longer texts as needed to maintain those properties.
Example¶
ExampleText prints a random key encoded in base32.
package mainimport ("crypto/rand""fmt")func main() {key := rand.Text()// The key is base32 and safe to display.fmt.Println(key)}Types¶
This section is empty.
Source Files