| .TH DES 1 "24 March 1987" |
| .SH NAME |
| des - DES file encryption |
| .SH SYNOPSIS |
| .PP |
| .B des -e|-d [-h] [-k key] [-b] |
| .SH DESCRIPTION |
| .B des |
| is a filter that encrypts or decrypts standard input to standard output |
| with the Data Encryption Standard (DES). |
| Either -e (encrypt) or -d (decrypt) must be specified. If the key is not |
| given on the command line with the -k option the command will prompt for it |
| twice, suppressing echo and comparing the two responses to guard against |
| mistyping. |
| .P |
| The -h flag controls how the key string is to be interpreted. |
| Without the -h flag, the key is an ASCII string. |
| Since DES ignores the low |
| order bit of each key byte, the |
| high order bit is set for odd parity, thus retaining the information contained |
| in the low order bit. |
| If the -h flag is set, the key string is interpreted as |
| 16 hex/ASCII characters; the low order bit of each byte is again ignored as per |
| the DES algorithm. |
| This allows the use of any arbitrary 56-bit key, including bytes representing |
| control characters that could not be typed if the -h option were not used. |
| .PP |
| By default, DES Cipher Block Chaining (CBC) mode is used, with an initial |
| vector (IV) of all zeros; if the -b option is specified, Electronic Code |
| Book (ECB) mode is used instead. |
| .PP |
| Except for the -h option, this command is compatible with the |
| .B des |
| command on the Sun Microsystems workstation. |
| .SH "SEE ALSO" |
| Sun Microsystems DES(1) manual page, which describes in detail how |
| the length of the file is encoded in the last block of ciphertext. |
| .SH AUTHOR |
| Phil Karn, KA9Q |
