sha2(3EXT) Extended Library Functions sha2(3EXT)NAME
sha2, SHA2Init, SHA2Update, SHA2Final, SHA256Init, SHA256Update,
SHA256Final, SHA384Init, SHA384Update, SHA384Final, SHA512Init,
SHA512Update, SHA512Final - SHA2 digest functions
SYNOPSIS
cc [ flag ... ] file ... -lmd [ library ... ]
#include <sha2.h>
void SHA2Init(uint64_t mech, SHA2_CTX *context);
void SHA2Update(SHA2_CTX *context, unsigned char *input,
unsigned int inlen);
void SHA2Final(unsigned char *output, SHA2_CTX *context);
void SHA256Init(SHA256_CTX *context);
void SHA256Update(SHA256_CTX *context, unsigned char *input,
unsigned int inlen);
void SHA256Final(unsigned char *output, SHA256_CTX *context);
void SHA384Init(SHA384_CTX *context);
void SHA384Update(SHA384_CTX *context, unsigned char *input,
unsigned int inlen);
void SHA384Final(unsigned char *output, 384_CTX *context);
void SHA512Init(SHA512_CTX *context);
void SHA512Update(SHA512_CTX *context, unsigned char *input,
unsigned int inlen);
void SHA512Final(unsigned char *output, 512_CTX *context);
DESCRIPTION
The SHA2Init(), SHA2Update(), SHA2Final() functions implement the
SHA256, SHA384 and SHA512 message-digest algorithms. The algorithms
take as input a message of arbitrary length and produces a 200-bit
"fingerprint" or "message digest" as output. The SHA2 message-digest
algorithms are intended for digital signature applications in which
large files are "compressed" in a secure manner before being encrypted
with a private (secret) key under a public-key cryptosystem such as
RSA.
SHA2Init(), SHA2Update(), SHA2Final()
The SHA2Init(), SHA2Update(), and SHA2Final() functions allow an
SHA2 digest to be computed over multiple message blocks. Between
blocks, the state of the SHA2 computation is held in an SHA2 con‐
text structure allocated by the caller. A complete digest computa‐
tion consists of calls to SHA2 functions in the following order:
one call to SHA2Init(), one or more calls to SHA2Update(), and one
call to SHA2Final().
The SHA2Init() function initializes the SHA2 context structure
pointed to by context. The mech argument is one of SHA256, SHA512,
SHA384.
The SHA2Update() function computes a partial SHA2 digest on the
inlen-byte message block pointed to by input, and updates the SHA2
context structure pointed to by context accordingly.
The SHA2Final() function generates the final SHA2Final digest,
using the SHA2 context structure pointed to by context. The SHA2
digest is written to output. After a call to SHA2Final(), the state
of the context structure is undefined. It must be reinitialized
with SHA2Init() before it can be used again.
SHA256Init(), SHA256Update(), SHA256Final(), SHA384Init(),
SHA384Update(), SHA384Final(), SHA512Init(), SHA512Update(),
SHA512Final()
Alternative APIs exist as named above. The Update() and Final()
sets of functions operate exactly as the previously described
SHA2Update() and SHA2Final() functions. The SHA256Init(),
SHA384Init(), and SHA512Init() functions do not take the mech argu‐
ment as it is implicit in the function names.
RETURN VALUES
These functions do not return a value.
EXAMPLES
Example 1 Authenticate a message found in multiple buffers
The following is a sample function that authenticates a message found
in multiple buffers. The calling function provides an authentication
buffer to contain the result of the SHA2 digest.
#include <sys/types.h>
#include <sys/uio.h>
#include <sha2.h>
int
AuthenticateMsg(unsigned char *auth_buffer, struct iovec
*messageIov, unsigned int num_buffers)
{
SHA2_CTX sha2_context;
unsigned int i;
SHA2Init(SHA384, &sha2_context);
for(i=0; i<num_buffers; i++)
{
SHA2Update(&sha2_context, messageIov->iov_base,
messageIov->iov_len);
messageIov += sizeof(struct iovec);
}
SHA2Final(auth_buffer, &sha2_context);
return 0;
}
Example 2 Authenticate a message found in multiple buffers
The following is a sample function that authenticates a message found
in multiple buffers. The calling function provides an authentication
buffer that will contain the result of the SHA384 digest, using alter‐
native interfaces.
int
AuthenticateMsg(unsigned char *auth_buffer, struct iovec
*messageIov, unsigned int num_buffers)
{
SHA384_CTX ctx;
unsigned int i;
SHA384Init(&ctx);
for(i=0, i<num_buffers; i++
{
SHA384Update(&ctx, messageIov->iov_base,
messageIov->iov_len);
messageIov += sizeof(struct iovec);
}
SHA384Final(auth_buffer, &ctx);
return 0;
}
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Committed │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOlibmd(3LIB)
FIPS 180-2
SunOS 5.10 13 Nov 2007 sha2(3EXT)
