SHAKE(3)

NAME
SHAKE - NIST FIPS PUB 202: SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions

SYNOPSIS
#include <sha3.h>
void
SHAKE128_Init(SHAKE128_CTX *ctx);
void
SHAKE128_Update(SHAKE128_CTX *ctx, const uint8_t *buf, size_t len);
void
SHAKE128_Final(uint8_t *output[], size_t outlen, SHAKE128_CTX *ctx);
void
SHAKE256_Init(SHAKE256_CTX *ctx);
void
SHAKE256_Update(SHAKE256_CTX *ctx, const uint8_t *buf, size_t len);
void
SHAKE256_Final(uint8_t *output[], size_t outlen, SHAKE256_CTX *ctx);

DESCRIPTION
The SHAKE functions implement the extendable-output functions of the NIST SHA-3 standard, FIPS PUB 202. The SHAKE functions absorb an arbitrary-length message m and yield an arbitrary-length output SHAKE128(m) or SHAKE256(m), truncated to a specified number of octets.

Before using the SHAKE functions, applications should first call SHA3_Selftest(3) and confirm that it succeeded.

Only the SHAKE128 functions are specified in detail; the SHAKE256 functions are analogous.

The caller must allocate memory for a SHAKE128_CTX object to hold the state of a SHAKE128 computation over a message. SHAKE128_CTX objects may be copied or relocated in memory.

SHAKE128_Init(ctx)
    Initialize a SHAKE128 context. Must be done before any other operations on ctx.

SHAKE128_Update(ctx, data, len)
    Append len octets at data to the message.

SHAKE128_Final(output, outlen, ctx)
    Store at output the first outlen octets of the SHAKE128 output for the message obtained by concatenating all prior inputs to SHAKE128_Update() on ctx.

    Subsequent use of ctx is not allowed, unless it is reinitialized with SHAKE128_Init().

SEE ALSO
keccak(3), sha3(3), SHA3_Selftest(3)

STANDARDS
National Institute of Standards and Technology, SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions, FIPS PUB 202, August 2015.

AUTHORS
Taylor R Campbell <campbell+sha3@mumble.net>