2 .\" ----------------------------------------------------------------------------
3 .\" "THE BEER-WARE LICENSE" (Revision 42):
4 .\" <phk@FreeBSD.org> wrote this file. As long as you retain this notice you
5 .\" can do whatever you want with this stuff. If we meet some day, and you think
6 .\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
7 .\" ----------------------------------------------------------------------------
9 .\" From: Id: mdX.3,v 1.14 1999/02/11 20:31:49 wollman Exp
30 .Nd calculate the FIPS 160 and 160-1 ``SHA'' message digests
37 .Fn SHA_Init "SHA_CTX *context"
39 .Fn SHA_Update "SHA_CTX *context" "const unsigned char *data" "size_t len"
41 .Fn SHA_Final "unsigned char digest[20]" "SHA_CTX *context"
43 .Fn SHA_End "SHA_CTX *context" "char *buf"
45 .Fn SHA_File "const char *filename" "char *buf"
47 .Fn SHA_FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"
49 .Fn SHA_Data "const unsigned char *data" "unsigned int len" "char *buf"
51 .Fn SHA1_Init "SHA_CTX *context"
53 .Fn SHA1_Update "SHA_CTX *context" "const unsigned char *data" "size_t len"
55 .Fn SHA1_Final "unsigned char digest[20]" "SHA_CTX *context"
57 .Fn SHA1_End "SHA_CTX *context" "char *buf"
59 .Fn SHA1_File "const char *filename" "char *buf"
61 .Fn SHA1_FileChunk "const char *filename" "char *buf" "off_t offset" "off_t length"
63 .Fn SHA1_Data "const unsigned char *data" "unsigned int len" "char *buf"
69 functions calculate a 160-bit cryptographic checksum (digest)
70 for any number of input bytes.
71 A cryptographic checksum is a one-way
72 hash function; that is, it is computationally impractical to find
73 the input corresponding to a particular output.
77 of the input-data, which does not disclose the actual input.
82 is the original Secure Hash Algorithm specified in
85 It was quickly proven insecure, and has been superseded by
88 is included for compatibility purposes only.
95 functions are the core functions.
100 run over the data with
102 and finally extract the result using
104 which will also erase the
110 which converts the return value to a 41-character
111 (including the terminating '\e0')
113 string which represents the 160 bits in hexadecimal.
116 calculates the digest of a file, and uses
118 to return the result.
119 If the file cannot be opened, a null pointer is returned.
123 but it only calculates the digest over a byte-range of the file specified,
131 parameter is specified as 0, or more than the length of the remaining part
134 calculates the digest from
138 calculates the digest of a chunk of data in memory, and uses
140 to return the result.
149 argument can be a null pointer, in which case the returned string
152 and subsequently must be explicitly deallocated using
157 argument is non-null it must point to at least 41 characters of buffer space.
166 These functions appeared in
169 The core hash routines were implemented by Eric Young based on the
174 No method is known to exist which finds two files having the same hash value,
175 nor to find a file with a specific hash value.
176 There is on the other hand no guarantee that such a method does not exist.
180 (Intel) implementation of
182 makes heavy use of the
184 instruction, which is not present on the original 80386.
187 on those processors will cause an illegal instruction trap.
188 (Arguably, the kernel should simply emulate this instruction.)