DragonFly On-Line Manual Pages

MD5(1)		       DragonFly General Commands Manual		MD5(1)


md5, sha1, sha256, rmd160 -- calculate a message-digest fingerprint (checksum) for a file


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 ...]


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.


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).


cksum(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.


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>. DragonFly 3.7 January 21, 2010 DragonFly 3.7