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Diffstat (limited to 'lib/libmd/sha.3')
| -rw-r--r-- | lib/libmd/sha.3 | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/lib/libmd/sha.3 b/lib/libmd/sha.3 new file mode 100644 index 0000000..5af126d --- /dev/null +++ b/lib/libmd/sha.3 @@ -0,0 +1,151 @@ +.\" +.\" ---------------------------------------------------------------------------- +.\" "THE BEER-WARE LICENSE" (Revision 42): +.\" <phk@login.dkuug.dk> wrote this file. As long as you retain this notice you +.\" can do whatever you want with this stuff. If we meet some day, and you think +.\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp +.\" ---------------------------------------------------------------------------- +.\" +.\" From: Id: mdX.3,v 1.14 1999/02/11 20:31:49 wollman Exp +.\" $FreeBSD$ +.\" +.Dd February 25, 1999 +.Dt SHA 3 +.Os FreeBSD 4.0 +.Sh NAME +.Nm SHA_Init , +.Nm SHA_Update , +.Nm SHA_Final , +.Nm SHA_End , +.Nm SHA_File , +.Nm SHA_Data , +.Nm SHA1_Init , +.Nm SHA1_Update , +.Nm SHA1_Final , +.Nm SHA1_End , +.Nm SHA1_File , +.Nm SHA1_Data +.Nd calculate the FIPS 160 and 160-1 ``SHA'' message digests +.Sh SYNOPSIS +.Fd #include <sys/types.h> +.Fd #include <sha.h> +.Ft void +.Fn SHA_Init "SHA_CTX *context" +.Ft void +.Fn SHA_Update "SHA_CTX *context" "const unsigned char *data" "unsigned int len" +.Ft void +.Fn SHA_Final "unsigned char digest[20]" "SHA_CTX *context" +.Ft "char *" +.Fn SHA_End "SHA_CTX *context" "char *buf" +.Ft "char *" +.Fn SHA_File "const char *filename" "char *buf" +.Ft "char *" +.Fn SHA_Data "const unsigned char *data" "unsigned int len" "char *buf" +.Ft void +.Fn SHA1_Init "SHA_CTX *context" +.Ft void +.Fn SHA1_Update "SHA_CTX *context" "const unsigned char *data" "unsigned int len" +.Ft void +.Fn SHA1_Final "unsigned char digest[20]" "SHA_CTX *context" +.Ft "char *" +.Fn SHA1_End "SHA_CTX *context" "char *buf" +.Ft "char *" +.Fn SHA1_File "const char *filename" "char *buf" +.Ft "char *" +.Fn SHA1_Data "const unsigned char *data" "unsigned int len" "char *buf" +.Sh DESCRIPTION +The +.Li SHA_ +and +.Li 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 doesn't disclose the actual +input. +.Pp +.Tn SHA +.Pq \&or Tn SHA-0 +is the original Secure Hash Algorithm specified in +.Tn FIPS +160. It was quickly proven insecure, and has been superseded by +.Tn SHA-1 . +.Tn SHA-0 +is included for compatibility purposes only. +.Pp +The +.Fn SHA1_Init , +.Fn SHA1_Update , +and +.Fn SHA1_Final +functions are the core functions. Allocate an SHA_CTX, initialize it with +.Fn SHA1_Init , +run over the data with +.Fn SHA1_Update , +and finally extract the result using +.Fn SHA1_Final . +.Pp +.Fn SHA1_End +is a wrapper for +.Fn SHA1_Final +which converts the return value to a 41-character +(including the terminating '\e0') +.Tn ASCII +string which represents the 160 bits in hexadecimal. +.Pp +.Fn SHA1_File +calculates the digest of a file, and uses +.Fn SHA1_End +to return the result. +If the file cannot be opened, a null pointer is returned. +.Fn SHA1_Data +calculates the digest of a chunk of data in memory, and uses +.Fn SHA1_End +to return the result. +.Pp +When using +.Fn SHA1_End , +.Fn SHA1_File , +or +.Fn SHA1_Data , +the +.Ar buf +argument can be a null pointer, in which case the returned string +is allocated with +.Xr malloc 3 +and subsequently must be explicitly deallocated using +.Xr free 3 +after use. +If the +.Ar buf +argument is non-null it must point to at least 41 characters of buffer space. +.Sh SEE ALSO +.Xr md2 3 , +.Xr md4 3 , +.Xr md5 3 , +.Xr ripemd 3 +.Sh AUTHORS +The core hash routines were implemented by Eric Young based on the +published +.Tn FIPS +standards. +.Sh HISTORY +These functions appeared in +.Fx 4.0 . +.Sh BUGS +No method is known to exist which finds two files having the same hash value, +nor to find a file with a specific hash value. +There is on the other hand no guarantee that such a method doesn't exist. +.Pp +The +.Tn IA32 +(Intel) implementation of +.Tn SHA-1 +makes heavy use of the +.Ql bswapl +instruction, which is not present on the original 80386. Attempts +to use +.Tn SHA-1 +on those processors will cause an illegal instruction trap. +(Arguably, the kernel should simply emulate this instruction.) |
