.TH SHA 1 "30 Apr 1993" .SH NAME sha \- Secure Hash Algorithm .SH SYNOPSIS .B "sha [-vt] [\fIfilename\fB]..." .SH DESCRIPTION .I Sha calculates the NIST Secure Hash Algorithm defined in FIPS 180. For each file in the list it produces 160 bits of hash, formatted as 40 hex digits. The "-v" flag causes .I sha to print the filename as well as the hash. The "-t" flag suppresses the spaces between 32-bit groups. If no file is specified, it processes the standard input. .PP NIST suggests using the Secure Hash Algorithm as a message digesting function, producing a message-dependent fixed-size block that may be securely signed with a digital signature system such as NIST's DSS. Quoting from the draft standard, "The SHA is designed to have the following properties: it is computationally infeasible to recover a message corresponding to a given message digest, or to find two different messages which produce the same message digest." .PP It may also be used as an ordinary file checksum. .SH "SEE ALSO" sum(1), sha_file(3), FIPS 180 .SH BUGS NIST defines SHA for arbitrary bit strings. This implementation operates only at the byte level. .SH AUTHOR Jim Gillogly