SHA2(3) | Library Functions Manual | SHA2(3) |
void
SHA224_Init(SHA224_CTX *context);
void
SHA224_Update(SHA224_CTX *context, const uint8_t *data, size_t len);
void
SHA224_Pad(SHA224_CTX *context);
void
SHA224_Final(uint8_t digest[SHA224_DIGEST_LENGTH], SHA224_CTX *context);
void
SHA224_Transform(uint32_t state[8], const uint8_t buffer[SHA224_BLOCK_LENGTH]);
char *
SHA224_End(SHA224_CTX *context, char *buf);
char *
SHA224_File(const char *filename, char *buf);
char *
SHA224_FileChunk(const char *filename, char *buf, off_t offset, off_t length);
char *
SHA224_Data(uint8_t *data, size_t len, char *buf);
void
SHA256_Init(SHA256_CTX *context);
void
SHA256_Update(SHA256_CTX *context, const uint8_t *data, size_t len);
void
SHA256_Pad(SHA256_CTX *context);
void
SHA256_Final(uint8_t digest[SHA256_DIGEST_LENGTH], SHA256_CTX *context);
void
SHA256_Transform(uint32_t state[8], const uint8_t buffer[SHA256_BLOCK_LENGTH]);
char *
SHA256_End(SHA256_CTX *context, char *buf);
char *
SHA256_File(const char *filename, char *buf);
char *
SHA256_FileChunk(const char *filename, char *buf, off_t offset, off_t length);
char *
SHA256_Data(uint8_t *data, size_t len, char *buf);
void
SHA384_Init(SHA384_CTX *context);
void
SHA384_Update(SHA384_CTX *context, const uint8_t *data, size_t len);
void
SHA384_Pad(SHA384_CTX *context);
void
SHA384_Final(uint8_t digest[SHA384_DIGEST_LENGTH], SHA384_CTX *context);
void
SHA384_Transform(uint64_t state[8], const uint8_t buffer[SHA384_BLOCK_LENGTH]);
char *
SHA384_End(SHA384_CTX *context, char *buf);
char *
SHA384_File(char *filename, char *buf);
char *
SHA384_FileChunk(char *filename, char *buf, off_t offset, off_t length);
char *
SHA384_Data(uint8_t *data, size_t len, char *buf);
void
SHA512_Init(SHA512_CTX *context);
void
SHA512_Update(SHA512_CTX *context, const uint8_t *data, size_t len);
void
SHA512_Pad(SHA512_CTX *context);
void
SHA512_Final(uint8_t digest[SHA512_DIGEST_LENGTH], SHA512_CTX *context);
void
SHA512_Transform(uint64_t state[8], const uint8_t buffer[SHA512_BLOCK_LENGTH]);
char *
SHA512_End(SHA512_CTX *context, char *buf);
char *
SHA512_File(char *filename, char *buf);
char *
SHA512_FileChunk(char *filename, char *buf, off_t offset, off_t length);
char *
SHA512_Data(uint8_t *data, size_t len, char *buf);
The SHA2 functions are considered to be more secure than the sha1(3) functions with which they share a similar interface. The 224, 256, 384, and 512-bit versions of SHA2 share the same interface. For brevity, only the 256-bit variants are described below.
The SHA256_Init() function initializes a SHA256_CTX context for use with SHA256_Update(), and SHA256_Final(). The SHA256_Update() function adds data of length len to the SHA256_CTX specified by context. SHA256_Final() is called when all data has been added via SHA256_Update() and stores a message digest in the digest parameter.
The SHA256_Pad() function can be used to apply padding to the message digest as in SHA256_Final(), but the current context can still be used with SHA256_Update().
The SHA256_Transform() function is used by SHA256_Update() to hash 512-bit blocks and forms the core of the algorithm. Most programs should use the interface provided by SHA256_Init(), SHA256_Update(), and SHA256_Final() instead of calling SHA256_Transform() directly.
The SHA256_End() function is a front end for SHA256_Final() which converts the digest into an ASCII representation of the digest in hexadecimal.
The SHA256_File() function calculates the digest for a file and returns the result via SHA256_End(). If SHA256_File() is unable to open the file, a NULL pointer is returned.
SHA256_FileChunk() behaves like SHA256_File() but calculates the digest only for that portion of the file starting at offset and continuing for length bytes or until end of file is reached, whichever comes first. A zero length can be specified to read until end of file. A negative length or offset will be ignored.
The SHA256_Data() function calculates the digest of an arbitrary string and returns the result via SHA256_End().
For each of the SHA256_End(), SHA256_File(), SHA256_FileChunk(), and SHA256_Data() functions the buf parameter should either be a string large enough to hold the resulting digest (e.g., SHA224_DIGEST_STRING_LENGTH, SHA256_DIGEST_STRING_LENGTH, SHA384_DIGEST_STRING_LENGTH, or SHA512_DIGEST_STRING_LENGTH, depending on the function being used) or a NULL pointer. In the latter case, space will be dynamically allocated via malloc(3) and should be freed using free(3) when it is no longer needed.
SHA256_CTX ctx; uint8_t results[SHA256_DIGEST_LENGTH]; char *buf; int n; buf = "abc"; n = strlen(buf); SHA256_Init(&ctx); SHA256_Update(&ctx, (uint8_t *)buf, n); SHA256_Final(results, &ctx); /* Print the digest as one long hex value */ printf("0x"); for (n = 0; n < SHA256_DIGEST_LENGTH; n++) printf("%02x", results[n]); putchar('\n');
Alternately, the helper functions could be used in the following way:
SHA256_CTX ctx; uint8_t output[SHA256_DIGEST_STRING_LENGTH]; char *buf = "abc"; printf("0x%s\n", SHA256_Data(buf, strlen(buf), output));
The SHA256_End(), SHA256_File(), SHA256_FileChunk(), and SHA256_Data() helper functions are derived from code written by Poul-Henning Kamp.
If a message digest is to be copied to a multi-byte type (i.e.: an array of five 32-bit integers) it will be necessary to perform byte swapping on little endian machines such as the i386, alpha, and vax.
May 20, 2009 | NetBSD 7.2 |