MD5(1) BSD General Commands Manual MD5(1)NAME
md5, sha1, sha256, rmd160 — calculate a message-digest fingerprint
(checksum) for a file
SYNOPSIS
md5 [-pqrtx] [-b offset] [-e offset] [-s string] [file ...]
sha1 [-pqrtx] [-b offset] [-e offset] [-s string] [file ...]
sha256 [-pqrtx] [-b offset] [-e offset] [-s string] [file ...]
rmd160 [-pqrtx] [-b offset] [-e offset] [-s string] [file ...]
DESCRIPTION
The md5, sha1, sha256 and rmd160 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 MD5, SHA-1, SHA-256 and RIPEMD-160 algorithms are intended for digi‐
tal 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.
MD5 has not yet (2001-09-03) been broken, but sufficient attacks have
been made that its security is in some doubt. The attacks on MD5 are in
the nature of finding “collisions” — that is, multiple inputs which hash
to the same value; it is still unlikely for an attacker to be able to
determine the exact original input given a hash value.
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.
-b offset
When processing file(s), use the specified begin and/or end
(below) instead of processing each file in its entirety. Either
option can be omitted. Both begin- and end-offsets can be speci‐
fied as just a number (of bytes) or be followed by K, M, or G to
mean that the number is to be multiplied by 1024 once, twice, or
thrice respectively. For example, to start at 512, you can use
-b 512 or -b 0.5K.
The use of offsets is implemented using mmap() and will only work
on regular files and mmap-able devices.
If the beginning offset is negative, its absolute value is sub‐
tracted from the file's size. Zero thus means the very beginning
of each file, which is also the default if the option is omitted
entirely.
-e offset
If the end-offset is not positive, its absolute value is sub‐
tracted from the file's size. Zero thus means the very end of
each file, which is also the default if the option is omitted
entirely.
-s string
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 -r
option.
-r Reverses the format of the output. This helps with visual diffs.
Does nothing when combined with the -ptx options.
-t Run a built-in time trial.
-x Run a built-in test script.
DIAGNOSTICS
The md5, sha1, sha256 and rmd160 utilities exit 0 on success, and
EX_NOINPUT (66) if at least one of the input files could not be read or
invalid offsets were specified. A mistake with command line arguments
results in EX_USAGE (64).
SEE ALSOcksum(1), mmap(2), md5(3), ripemd(3), sha(3)
R. Rivest, The MD5 Message-Digest Algorithm, RFC 1321.
J. Burrows, The Secure Hash Standard, FIPS PUB 180-1.
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/publications/fips/fips180-2/fips180-2withchangenotice.pdf.
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⟩.
BSD January 21, 2010 BSD
