1 .TH ENCRYPT 3
2 .SH NAME
3 encrypt, decrypt, netcrypt \- DES encryption
4 .SH SYNOPSIS
5 .B #include <u.h>
6 .br
7 .B #include <libc.h>
8 .PP
9 .B
10 int	encrypt(void *key, void *data, int len)
11 .PP
12 .B
13 int	decrypt(void *key, void *data, int len)
14 .PP
15 .B
16 int	netcrypt(void *key, void *data)
17 .SH DESCRIPTION
18 .I Encrypt
19 and
20 .I decrypt
21 perform DES encryption and decryption.
22 .I Key
23 is an array of
24 .B DESKEYLEN
25 (defined as 7 in
26 .BR <auth.h> )
27 bytes containing the encryption key.
28 .I Data
29 is an array of
30 .I len
31 bytes;
32 it must be at least 8 bytes long.
33 The bytes are encrypted or decrypted in place.
34 .PP
35 The DES algorithm encrypts an individual 8-byte block of data.
36 .I Encrypt
37 uses the following method to encrypt data longer than 8 bytes.
38 The first 8 bytes are encrypted as usual.
39 The last byte of the encrypted result
40 is prefixed to the next 7 unencrypted bytes to make the next 8
41 bytes to encrypt.
42 This is repeated until fewer than 7 bytes remain unencrypted.
43 Any remaining unencrypted bytes are encrypted with enough of the preceding
44 encrypted bytes to make a full 8-byte block.
45 .I Decrypt
46 uses the inverse algorithm.
47 .PP
48 .I Netcrypt
49 performs the same encryption as a SecureNet Key.
50 .I Data
51 points to an
52 .SM ASCII
53 string of decimal digits with numeric value between 0 and 10000.
54 These digits are copied into an 8-byte buffer with trailing binary zero fill
55 and encrypted as one DES block.
56 The first four bytes are each formatted as two digit
57 .SM ASCII
58 hexadecimal numbers,
59 and the string is copied into
60 .IR data .
61 .SH SOURCE
62 .B \*9/src/lib9
63 .SH DIAGNOSTICS
64 These routines return 1 if the data was encrypted,
65 and 0 if the encryption fails.
66 .I Encrypt
67 and
68 .I decrypt
69 fail if the data passed is less than 8 bytes long.
70 .I Netcrypt
71 can fail if it is passed invalid data.
72 .\" .SH SEE ALSO
73 .\" .IR securenet (8)
74 .SH BUGS
75 The implementation is broken in a way that makes
76 it unsuitable for anything but authentication.
77 .PP
78 To avoid name conflicts with the underlying system,
79 .IR encrypt 
80 and
81 .IR decrypt
82 are preprocessor macros defined as
83 .IR p9encrypt
84 and
85 .IR p9decrypt ;
86 see
87 .MR intro (3) .