drbg

Documentation

Overview

Package drbg provides cryptographically secure random bytes usable by FIPS code. In FIPS mode it uses an SP 800-90A Rev. 1 Deterministic Random Bit Generator (DRBG). Otherwise, it uses the operating system's random number generator.

Index

• Constants
• func Read(b []byte)
• func ReadWithReader(r io.Reader, b []byte) error
• func ReadWithReaderDeterministic(r io.Reader, b []byte) error
• type Counter
  • func NewCounter(entropy *[SeedSize]byte) *Counter
  • func (c *Counter) Generate(out []byte, additionalInput *[SeedSize]byte) (reseedRequired bool)
  • func (c *Counter) Reseed(entropy, additionalInput *[SeedSize]byte)
• type DefaultReader

Constants

const (
	SeedSize = keySize + aes.BlockSize
)

Functions

func Read

func Read(b []byte)

Read fills b with cryptographically secure random bytes. In FIPS mode, it uses an SP 800-90A Rev. 1 Deterministic Random Bit Generator (DRBG). Otherwise, it uses the operating system's random number generator.

func ReadWithReader

func ReadWithReader(r io.Reader, b []byte) error

ReadWithReader uses Reader to fill b with cryptographically secure random bytes. It is intended for use in APIs that expose a rand io.Reader.

If Reader is not the default Reader from crypto/rand, randutil.MaybeReadByte and fips140.RecordNonApproved are called.

func ReadWithReaderDeterministic

func ReadWithReaderDeterministic(r io.Reader, b []byte) error

ReadWithReaderDeterministic is like ReadWithReader, but it doesn't call randutil.MaybeReadByte on non-default Readers.

Types

type Counter

type Counter struct {
	// contains filtered or unexported fields
}

Counter is an SP 800-90A Rev. 1 CTR_DRBG instantiated with AES-256.

Per Table 3, it has a security strength of 256 bits, a seed size of 384 bits, a counter length of 128 bits, a reseed interval of 2^48 requests, and a maximum request size of 2^19 bits (2^16 bytes, 64 KiB).

We support a narrow range of parameters that fit the needs of our RNG: AES-256, no derivation function, no personalization string, no prediction resistance, and 384-bit additional input.

WARNING: this type provides tightly scoped support for the DRBG functionality we need for FIPS 140-3 _only_. This type _should not_ be used outside of the FIPS 140-3 module for any other use.

In particular, as documented, Counter does not support the derivation function, or personalization strings which are necessary for safely using this DRBG for generic purposes without leaking sensitive values.

func NewCounter

func NewCounter(entropy *[SeedSize]byte) *Counter

func (*Counter) Generate

func (c *Counter) Generate(out []byte, additionalInput *[SeedSize]byte) (reseedRequired bool)

Generate produces at most maxRequestSize bytes of random data in out.

func (*Counter) Reseed

func (c *Counter) Reseed(entropy, additionalInput *[SeedSize]byte)

type DefaultReader

type DefaultReader interface {
	// contains filtered or unexported methods
}

DefaultReader is a sentinel type, embedded in the default crypto/rand.Reader, used to recognize it when passed to APIs that accept a rand io.Reader.