1.\" $FreeBSD: src/sbin/md5/md5.1,v 1.10.2.7 2002/06/20 23:09:06 charnier Exp $ 2.Dd February 14, 1994 3.Dt MD5 1 4.Os 5.Sh NAME 6.Nm md5 7.Nd calculate a message-digest fingerprint (checksum) for a file 8.Sh SYNOPSIS 9.Nm 10.Op Fl pqrtx 11.Op Fl s Ar string 12.Op Ar 13.Sh DESCRIPTION 14The 15.Nm 16utility takes as input a message of arbitrary length and produces 17as output a 128-bit 18.Dq fingerprint 19or 20.Dq message digest 21of the input. 22It is conjectured that it is computationally infeasible to 23produce two messages having the same message digest, or to produce any 24message having a given prespecified target message digest. 25The MD5 algorithm is intended for digital signature applications, where a 26large file must be 27.Dq compressed 28in a secure manner before being encrypted with a private 29(secret) 30key under a public-key cryptosystem such as 31.Em RSA . 32.Pp 33MD5 has not yet (2001-09-03) been broken, but sufficient attacks have been 34made that its security is in some doubt. 35The attacks on MD5 36are in the nature of finding 37.Dq collisions 38\(em that is, multiple 39inputs which hash to the same value; it is still unlikely for an attacker 40to be able to determine the exact original input given a hash value. 41.Pp 42The following options may be used in any combination and must 43precede any files named on the command line. 44The MD5 45sum of each file listed on the command line is printed after the options 46are processed. 47.Bl -tag -width indent 48.It Fl s Ar string 49Print a checksum of the given 50.Ar string . 51.It Fl p 52Echo stdin to stdout and appends the MD5 sum to stdout. 53.It Fl q 54Quiet mode - only the MD5 sum is printed out. 55Overrides the 56.Fl r 57option. 58.It Fl r 59Reverses the format of the output. 60This helps with visual diffs. 61Does nothing 62when combined with the 63.Fl ptx 64options. 65.It Fl t 66Run a built-in time trial. 67.It Fl x 68Run a built-in test script. 69.El 70.Sh SEE ALSO 71.Xr cksum 1 72.Rs 73.%A R. Rivest 74.%T The MD5 Message-Digest Algorithm 75.%O RFC1321 76.Re 77.Sh ACKNOWLEDGMENTS 78This program is placed in the public domain for free general use by 79RSA Data Security. 80