1CRYPT(1) General Commands Manual CRYPT(1)
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6 crypt - encode/decode
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9 crypt [ password ]
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12 Crypt reads from the standard input and writes on the standard output.
13 The password is a key that selects a particular transformation. If no
14 password is given, crypt demands a key from the terminal and turns off
15 printing while the key is being typed in. Crypt encrypts and decrypts
16 with the same key:
17 crypt key <clear >cypher
19 crypt key <cypher | pr
20 will print the clear.
22 Files encrypted by crypt are compatible with those treated by the edi‐
24 tor ed in encryption mode.
25 The security of encrypted files depends on three factors: the fundamen‐
27 tal method must be hard to solve; direct search of the key space must
28 be infeasible; `sneak paths' by which keys or cleartext can become vis‐
29 ible must be minimized.
30 Crypt implements a one-rotor machine designed along the lines of the
32 German Enigma, but with a 256-element rotor. Methods of attack on such
33 machines are known, but not widely; moreover the amount of work
34 required is likely to be large.
35 The transformation of a key into the internal settings of the machine
37 is deliberately designed to be expensive, i.e. to take a substantial
38 fraction of a second to compute. However, if keys are restricted to
39 (say) three lower-case letters, then encrypted files can be read by
40 expending only a substantial fraction of five minutes of machine time.
41 Since the key is an argument to the crypt command, it is potentially
43 visible to users executing ps(1) or a derivative. To minimize this
44 possibility, crypt takes care to destroy any record of the key immedi‐
45 ately upon entry. No doubt the choice of keys and key security are the
46 most vulnerable aspect of crypt.
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49 /dev/tty for typed key
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52 ed(1), makekey(8)
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55 There is no warranty of merchantability nor any warranty of fitness for
56 a particular purpose nor any other warranty, either express or implied,
57 as to the accuracy of the enclosed materials or as to their suitability
58 for any particular purpose. Accordingly, Bell Telephone Laboratories
59 assumes no responsibility for their use by the recipient. Further,
60 Bell Laboratories assumes no obligation to furnish any assistance of
61 any kind whatsoever, or to furnish any additional information or docu‐
62 mentation.
63 CRYPT(1)