NAME
SHA_Init,
SHA_Update, SHA_Final,
SHA_End, SHA_Fd,
SHA_FdChunk, SHA_File,
SHA_FileChunk, SHA_Data,
SHA1_Init, SHA1_Update,
SHA1_Final, SHA1_End,
SHA1_Fd, SHA1_FdChunk,
SHA1_File, SHA1_FileChunk,
SHA1_Data —
calculate the FIPS 160 and 160-1
``SHA'' message digests
LIBRARY
Message Digest (MD4, MD5, etc.) Support Library (libmd, -lmd)
SYNOPSIS
#include
<sys/types.h>
#include <sha.h>
void
SHA_Init(SHA_CTX
*context);
void
SHA_Update(SHA_CTX
*context, const unsigned
char *data, size_t
len);
void
SHA_Final(unsigned
char digest[20], SHA_CTX
*context);
char *
SHA_End(SHA_CTX
*context, char
*buf);
char *
SHA_Fd(int
fd, char *buf);
char *
SHA_FdChunk(int
fd, char *buf,
off_t offset,
off_t length);
char *
SHA_File(const
char *filename, char
*buf);
char *
SHA_FileChunk(const
char *filename, char
*buf, off_t offset,
off_t length);
char *
SHA_Data(const
unsigned char *data,
unsigned int len,
char *buf);
void
SHA1_Init(SHA_CTX
*context);
void
SHA1_Update(SHA_CTX
*context, const unsigned
char *data, size_t
len);
void
SHA1_Final(unsigned
char digest[20], SHA_CTX
*context);
char *
SHA1_End(SHA_CTX
*context, char
*buf);
char *
SHA1_Fd(int
fd, char *buf);
char *
SHA1_FdChunk(int
fd, char *buf,
off_t offset,
off_t length);
char *
SHA1_File(const
char *filename, char
*buf);
char *
SHA1_FileChunk(const
char *filename, char
*buf, off_t offset,
off_t length);
char *
SHA1_Data(const
unsigned char *data,
unsigned int len,
char *buf);
DESCRIPTION
The SHA_ and SHA1_
functions calculate a 160-bit cryptographic checksum (digest) for any number
of input bytes. A cryptographic checksum is a one-way hash function; that
is, it is computationally impractical to find the input corresponding to a
particular output. This net result is a “fingerprint” of the
input-data, which does not disclose the actual input.
SHA (or SHA-0) is the original Secure Hash Algorithm specified in FIPS 160. It was quickly proven insecure, and has been superseded by SHA-1. SHA-0 is included for compatibility purposes only.
The
SHA1_Init(),
SHA1_Update(),
and SHA1_Final() functions are the core functions.
Allocate an SHA_CTX, initialize it with
SHA1_Init(), run over the data with
SHA1_Update(), and finally extract the result using
SHA1_Final(), which will also erase the
SHA_CTX.
SHA1_End()
is a wrapper for
SHA1_Final()
which converts the return value to a 41-character (including the terminating
'\0') ASCII string which represents the 160 bits in hexadecimal.
SHA1_File()
calculates the digest of a file, and uses SHA1_End()
to return the result. If the file cannot be opened, a null pointer is
returned.
SHA1_FileChunk()
is similar to SHA1_File(), but it only calculates
the digest over a byte-range of the file specified, starting at
offset and spanning length
bytes. If the length parameter is specified as 0, or
more than the length of the remaining part of the file,
SHA1_FileChunk() calculates the digest from
offset to the end of file.
SHA1_Data() calculates the digest of a chunk of data
in memory, and uses SHA1_End() to return the
result.
The
SHA1_Fd()
and
SHA1_FdChunk()
functions are identical to their SHA1_File() and
SHA1_FileChunk() counterparts, with the exception
that the first argument is an fd instead of a
filename.
When using
SHA1_End(),
SHA1_File(), or
SHA1_Data(),
the buf argument can be a null pointer, in which case
the returned string is allocated with
malloc(3) and subsequently must be explicitly deallocated
using free(3) after use. If the buf argument
is non-null it must point to at least 41 characters of buffer space.
ERRORS
The SHA1_End() function called with a null
buf argument may fail and return NULL if:
- [
ENOMEM] - Insufficient storage space is available.
The SHA1_File() and
SHA1_FileChunk() may return NULL when underlying
open(2),
fstat(2),
lseek(2), or
SHA1_End(3) fail.
SEE ALSO
HISTORY
These functions appeared in FreeBSD 4.0.
AUTHORS
The core hash routines were implemented by Eric Young based on the published FIPS standards.
BUGS
The SHA1 algorithm has been proven to be vulnerable to practical collision attacks and should not be relied upon to produce unique outputs, nor should it be used as part of a new cryptographic signature scheme.