NAME
md5, sha1,
sha224, sha256,
sha384, sha512,
sha512t256, rmd160,
skein256, skein512,
skein1024 —
calculate a message-digest fingerprint
(checksum) for a file
SYNOPSIS
md5 |
[-pqrtx] [-c
string] [-s
string] [file ...]
(All other hashes have the same options and usage.) |
DESCRIPTION
Themd5, sha1,
sha224, sha256,
sha384, sha512, sha512t256,
rmd160, skein256, skein512, and
skein1024 utilities take as input a message of
arbitrary length and produce as output a “fingerprint” or
“message digest” of the input. It is conjectured that it is
computationally infeasible to produce two messages having the same message
digest, or to produce any message having a given prespecified target message
digest. The SHA-224, SHA-256, SHA-384, SHA-512, RIPEMD-160, and SKEIN
algorithms are intended for digital signature applications, where a large file
must be “compressed” in a secure manner before being encrypted
with a private (secret) key under a public-key cryptosystem such as RSA.
The MD5 and SHA-1 algorithms have been proven to be vulnerable to practical collision attacks and should not be relied upon to produce unique outputs, nor should they be used as part of a cryptographic signature scheme. As of 2017-03-02, there is no publicly known method to reverse either algorithm, i.e. to find an input that produces a specific output.
SHA-512t256 is a version of SHA-512 truncated to only 256 bits. On 64-bit hardware, this algorithm is approximately 50% faster than SHA-256 but with the same level of security. The hashes are not interchangeable.
It is recommended that all new applications use SHA-512 or SKEIN-512 instead of one of the other hash functions.
The following options may be used in any combination and must precede any files named on the command line. The hexadecimal checksum of each file listed on the command line is printed after the options are processed.
-cstring- Compare the digest of the file against this string. (Note that this option is not yet useful if multiple files are specified.)
-sstring- Print a checksum of the given string.
-p- Echo stdin to stdout and append the checksum to stdout.
-q- Quiet mode — only the checksum is printed out. Overrides the
-roption. -r- Reverses the format of the output. This helps with visual diffs. Does
nothing when combined with the
-ptxoptions. -t- Run a built-in time trial.
-x- Run a built-in test script.
EXIT STATUS
The md5, sha1,
sha224, sha256,
sha512, sha512t256,
rmd160, skein256,
skein512, and skein1024
utilities exit 0 on success, 1 if at least one of the input files could not
be read, and 2 if at least one file does not have the same hash as the
-c option.
SEE ALSO
cksum(1), md5(3), ripemd(3), sha(3), sha224(3), sha256(3), sha384(3), sha512(3), skein(3)
R. Rivest, The MD5 Message-Digest Algorithm, RFC1321.
J. Burrows, The Secure Hash Standard, FIPS PUB 180-2.
D. Eastlake and P. Jones, US Secure Hash Algorithm 1, RFC 3174.
RIPEMD-160 is part of the ISO draft standard "ISO/IEC DIS 10118-3" on dedicated hash functions.
Secure Hash Standard (SHS): http://csrc.nist.gov/cryptval/shs.html.
The RIPEMD-160 page: http://www.esat.kuleuven.ac.be/~bosselae/ripemd160.html.
ACKNOWLEDGMENTS
This program is placed in the public domain for free general use by RSA Data Security.
Support for SHA-1 and RIPEMD-160 has been added by Oliver Eikemeier <eik@FreeBSD.org>.