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	crypt.c - 9base - revived minimalist port of Plan 9 userland to Unix
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	---
	crypt.c (1045B)
	---
	1 /*
	2 * Data Encryption Standard
	3 * D.P.Mitchell 83/06/08.
	4 *
	5 * block_cipher(key, block, decrypting)
	6 *
	7 * these routines use the non-standard 7 byte format
	8 * for DES keys.
	9 */
	10 #include <u.h>
	11 #include <libc.h>
	12 #include <auth.h>
	13 #include <libsec.h>
	14
	15 /*
	16 * destructively encrypt the buffer, which
	17 * must be at least 8 characters long.
	18 */
	19 int
	20 encrypt(void key, void vbuf, int n)
	21 {
	22 ulong ekey[32];
	23 uchar *buf;
	24 int i, r;
	25
	26 if(n < 8)
	27 return 0;
	28 key_setup(key, ekey);
	29 buf = vbuf;
	30 n--;
	31 r = n % 7;
	32 n /= 7;
	33 for(i = 0; i < n; i++){
	34 block_cipher(ekey, buf, 0);
	35 buf += 7;
	36 }
	37 if(r)
	38 block_cipher(ekey, buf - 7 + r, 0);
	39 return 1;
	40 }
	41
	42 /*
	43 * destructively decrypt the buffer, which
	44 * must be at least 8 characters long.
	45 */
	46 int
	47 decrypt(void key, void vbuf, int n)
	48 {
	49 ulong ekey[128];
	50 uchar *buf;
	51 int i, r;
	52
	53 if(n < 8)
	54 return 0;
	55 key_setup(key, ekey);
	56 buf = vbuf;
	57 n--;
	58 r = n % 7;
	59 n /= 7;
	60 buf += n * 7;
	61 if(r)
	62 block_cipher(ekey, buf - 7 + r, 1);
	63 for(i = 0; i < n; i++){
	64 buf -= 7;
	65 block_cipher(ekey, buf, 1);
	66 }
	67 return 1;
	68 }