1.\" $FreeBSD$ 2.Dd June 15, 2020 3.Dt MD5 1 4.Os 5.Sh NAME 6.Nm md5 , sha1 , sha224 , sha256 , sha384 , sha512 , sha512t256 , rmd160 , 7.Nm skein256 , skein512 , skein1024 8.Nd calculate a message-digest fingerprint (checksum) for a file 9.Sh SYNOPSIS 10.Nm 11.Op Fl pqrtx 12.Op Fl c Ar string 13.Op Fl s Ar string 14.Op Ar 15.Pp 16(All other hashes have the same options and usage.) 17.Sh DESCRIPTION 18The 19.Nm md5 , sha1 , sha224 , sha256 , sha384 , sha512 , sha512t256 , rmd160 , 20.Nm skein256 , skein512 , 21and 22.Nm skein1024 23utilities take as input a message of arbitrary length and produce as 24output a 25.Dq fingerprint 26or 27.Dq message digest 28of the input. 29It is conjectured that it is computationally infeasible to 30produce two messages having the same message digest, or to produce any 31message having a given prespecified target message digest. 32The SHA-224 , SHA-256 , SHA-384 , SHA-512, RIPEMD-160, 33and SKEIN 34algorithms are intended for digital signature applications, where a 35large file must be 36.Dq compressed 37in a secure manner before being encrypted with a private 38(secret) 39key under a public-key cryptosystem such as RSA. 40.Pp 41The MD5 and SHA-1 algorithms have been proven to be vulnerable to practical 42collision attacks and should not be relied upon to produce unique outputs, 43.Em nor should they be used as part of a cryptographic signature scheme. 44As of 2017-03-02, there is no publicly known method to 45.Em reverse 46either algorithm, i.e., to find an input that produces a specific 47output. 48.Pp 49SHA-512t256 is a version of SHA-512 truncated to only 256 bits. 50On 64-bit hardware, this algorithm is approximately 50% faster than SHA-256 but 51with the same level of security. 52The hashes are not interchangeable. 53.Pp 54It is recommended that all new applications use SHA-512 or SKEIN-512 55instead of one of the other hash functions. 56.Pp 57The following options may be used in any combination and must 58precede any files named on the command line. 59The hexadecimal checksum of each file listed on the command line is printed 60after the options are processed. 61.Bl -tag -width indent 62.It Fl c Ar string 63Compare the digest of the file against this string. 64.Pq Note that this option is not yet useful if multiple files are specified. 65.It Fl s Ar string 66Print a checksum of the given 67.Ar string . 68.It Fl p 69Echo stdin to stdout and append the checksum to stdout. 70.It Fl q 71Quiet mode \(em only the checksum is printed out. 72Overrides the 73.Fl r 74option. 75.It Fl r 76Reverses the format of the output. 77This helps with visual diffs. 78Does nothing 79when combined with the 80.Fl ptx 81options. 82.It Fl t 83Run a built-in time trial. 84.It Fl x 85Run a built-in test script. 86.El 87.Sh EXIT STATUS 88The 89.Nm md5 , sha1 , sha224 , sha256 , sha512 , sha512t256 , rmd160 , 90.Nm skein256 , skein512 , 91and 92.Nm skein1024 93utilities exit 0 on success, 941 if at least one of the input files could not be read, 95and 2 if at least one file does not have the same hash as the 96.Fl c 97option. 98.Sh SEE ALSO 99.Xr cksum 1 , 100.Xr md5 3 , 101.Xr ripemd 3 , 102.Xr sha 3 , 103.Xr sha256 3 , 104.Xr sha384 3 , 105.Xr sha512 3 , 106.Xr skein 3 107.Rs 108.%A R. Rivest 109.%T The MD5 Message-Digest Algorithm 110.%O RFC1321 111.Re 112.Rs 113.%A J. Burrows 114.%T The Secure Hash Standard 115.%O FIPS PUB 180-2 116.Re 117.Rs 118.%A D. Eastlake and P. Jones 119.%T US Secure Hash Algorithm 1 120.%O RFC 3174 121.Re 122.Pp 123RIPEMD-160 is part of the ISO draft standard 124.Qq ISO/IEC DIS 10118-3 125on dedicated hash functions. 126.Pp 127Secure Hash Standard (SHS): 128.Pa http://csrc.nist.gov/cryptval/shs.html . 129.Pp 130The RIPEMD-160 page: 131.Pa http://www.esat.kuleuven.ac.be/~bosselae/ripemd160.html . 132.Sh ACKNOWLEDGMENTS 133This program is placed in the public domain for free general use by 134RSA Data Security. 135.Pp 136Support for SHA-1 and RIPEMD-160 has been added by 137.An Oliver Eikemeier Aq Mt eik@FreeBSD.org . 138