1.\" $FreeBSD: src/sbin/md5/md5.1,v 1.10.2.7 2002/06/20 23:09:06 charnier Exp $ 2.\" $DragonFly: src/sbin/md5/md5.1,v 1.2 2003/06/17 04:27:33 dillon Exp $ 3.Dd February 14, 1994 4.Dt MD5 1 5.Os 6.Sh NAME 7.Nm md5 8.Nd calculate a message-digest fingerprint (checksum) for a file 9.Sh SYNOPSIS 10.Nm 11.Op Fl pqrtx 12.Op Fl s Ar string 13.Op Ar 14.Sh DESCRIPTION 15The 16.Nm 17utility takes as input a message of arbitrary length and produces 18as output a 128-bit 19.Dq fingerprint 20or 21.Dq message digest 22of the input. 23It is conjectured that it is computationally infeasible to 24produce two messages having the same message digest, or to produce any 25message having a given prespecified target message digest. 26The MD5 algorithm is intended for digital signature applications, where a 27large file must be 28.Dq compressed 29in a secure manner before being encrypted with a private 30(secret) 31key under a public-key cryptosystem such as 32.Em RSA . 33.Pp 34MD5 has not yet (2001-09-03) been broken, but sufficient attacks have been 35made that its security is in some doubt. 36The attacks on MD5 37are in the nature of finding 38.Dq collisions 39\(em that is, multiple 40inputs which hash to the same value; it is still unlikely for an attacker 41to be able to determine the exact original input given a hash value. 42.Pp 43The following options may be used in any combination and must 44precede any files named on the command line. 45The MD5 46sum of each file listed on the command line is printed after the options 47are processed. 48.Bl -tag -width indent 49.It Fl s Ar string 50Print a checksum of the given 51.Ar string . 52.It Fl p 53Echo stdin to stdout and appends the MD5 sum to stdout. 54.It Fl q 55Quiet mode - only the MD5 sum is printed out. 56Overrides the 57.Fl r 58option. 59.It Fl r 60Reverses the format of the output. 61This helps with visual diffs. 62Does nothing 63when combined with the 64.Fl ptx 65options. 66.It Fl t 67Run a built-in time trial. 68.It Fl x 69Run a built-in test script. 70.El 71.Sh SEE ALSO 72.Xr cksum 1 73.Rs 74.%A R. Rivest 75.%T The MD5 Message-Digest Algorithm 76.%O RFC1321 77.Re 78.Sh ACKNOWLEDGMENTS 79This program is placed in the public domain for free general use by 80RSA Data Security. 81