1.\" $FreeBSD$ 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 14.Nm Md5 15takes as input a message of arbitrary length and produces 16as output a 128-bit 17.Dq fingerprint 18or 19.Dq message digest 20of the input. 21It is conjectured that it is computationally infeasible to 22produce two messages having the same message digest, or to produce any 23message having a given prespecified target message digest. 24The MD5 algorithm is intended for digital signature applications, where a 25large file must be 26.Dq compressed 27in a secure manner before being encrypted with a private 28(secret) 29key under a public-key cryptosystem such as 30.Em RSA . 31.Pp 32MD5 has not yet (2001-09-03) been broken, but sufficient attacks have been 33made that its security is in some doubt. 34The attacks on MD5 35are in the nature of finding 36.Dq collisions 37\(em that is, multiple 38inputs which hash to the same value; it is still unlikely for an attacker 39to be able to determine the exact original input given a hash value. 40.Pp 41The following options may be used in any combination and must 42precede any files named on the command line. 43The MD5 44sum of each file listed on the command line is printed after the options 45are processed. 46.Bl -tag -width indent 47.It Fl s Ar string 48Print a checksum of the given 49.Ar string . 50.It Fl p 51Echo stdin to stdout and appends the MD5 sum to stdout. 52.It Fl q 53Quiet mode - only the MD5 sum is printed out. 54Overrides the 55.Fl r 56option. 57.It Fl r 58Reverses the format of the output. 59This helps with visual diffs. 60Does nothing 61when combined with the 62.Fl ptx 63options. 64.It Fl t 65Run a built-in time trial. 66.It Fl x 67Run a built-in test script. 68.El 69.Sh SEE ALSO 70.Xr cksum 1 71.Rs 72.%A R. Rivest 73.%T The MD5 Message-Digest Algorithm 74.%O RFC1321 75.Re 76.Sh ACKNOWLEDGMENTS 77This program is placed in the public domain for free general use by 78RSA Data Security. 79