32v 1m crypt
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CRYPT(1) UNIX Programmer's Manual CRYPT(1)
crypt - encode/decode
crypt [ password ]
_C_r_y_p_t reads from the standard input and writes on the stan- dard output. The _p_a_s_s_w_o_r_d is a key that selects a particu- lar transformation. If no _p_a_s_s_w_o_r_d is given, _c_r_y_p_t demands a key from the terminal and turns off printing while the key is being typed in. _C_r_y_p_t encrypts and decrypts with the same key:
crypt key <clear >cypher crypt key <cypher | pr
will print the clear.
Files encrypted by _c_r_y_p_t are compatible with those treated by the editor _e_d in encryption mode.
The security of encrypted files depends on three factors: the fundamental method must be hard to solve; direct search of the key space must be infeasible; `sneak paths' by which keys or cleartext can become visible must be minimized.
_C_r_y_p_t implements a one-rotor machine designed along the lines of the German Enigma, but with a 256-element rotor. Methods of attack on such machines are known, but not widely; moreover the amount of work required is likely to be large.
The transformation of a key into the internal settings of the machine is deliberately designed to be expensive, i.e. to take a substantial fraction of a second to compute. How- ever, if keys are restricted to (say) three lower-case letters, then encrypted files can be read by expending only a substantial fraction of five minutes of machine time.
Since the key is an argument to the _c_r_y_p_t command, it is potentially visible to users executing _p_s(1) or a deriva- tive. To minimize this possibility, _c_r_y_p_t takes care to destroy any record of the key immediately upon entry. No doubt the choice of keys and key security are the most vulnerable aspect of _c_r_y_p_t.
/dev/tty for typed key
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