encrypt, decrypt, netcrypt - DES encryption
#include <u.h>
#include <libc.h>
int encrypt(void *key, void *data, int len)
int decrypt(void *key, void *data, int len)
int netcrypt(void *key, void *data)
Encrypt and
decrypt perform DES encryption and decryption.
Key is an array of
DESKEYLEN (defined as 7 in
<auth.h>) bytes containing the encryption key.
Data is an
array of
len bytes; it must be at least 8 bytes long. The bytes are
encrypted or decrypted in place.
The DES algorithm encrypts an individual 8-byte block of data.
Encrypt
uses the following method to encrypt data longer than 8 bytes. The first 8
bytes are encrypted as usual. The last byte of the encrypted result is
prefixed to the next 7 unencrypted bytes to make the next 8 bytes to encrypt.
This is repeated until fewer than 7 bytes remain unencrypted. Any remaining
unencrypted bytes are encrypted with enough of the preceding encrypted bytes
to make a full 8-byte block.
Decrypt uses the inverse algorithm.
Netcrypt performs the same encryption as a SecureNet Key.
Data
points to an
ASCII string of decimal digits with numeric value
between 0 and 10000. These digits are copied into an 8-byte buffer with
trailing binary zero fill and encrypted as one DES block. The first four bytes
are each formatted as two digit
ASCII hexadecimal numbers, and
the string is copied into
data.
/src/lib9
These routines return 1 if the data was encrypted, and 0 if the encryption
fails.
Encrypt and
decrypt fail if the data passed is less than
8 bytes long.
Netcrypt can fail if it is passed invalid data.
The implementation is broken in a way that makes it unsuitable for anything but
authentication.
To avoid name conflicts with the underlying system,
encrypt and
decrypt are preprocessor macros defined as
p9encrypt and
p9decrypt; see
intro(3).