Plan 9 from Bell Labs’s /usr/web/sources/plan9/sys/src/cmd/unix/drawterm/libsec/des3ECB.c

Copyright © 2021 Plan 9 Foundation.
Distributed under the MIT License.
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#include "os.h"
#include <mp.h>
#include <libsec.h>

// I wasn't sure what to do when the buffer was not
// a multiple of 8.  I did what lacy's cryptolib did
// to be compatible, but it looks dangerous to me
// since its encrypting plain text with the key. -- presotto

void
des3ECBencrypt(uchar *p, int len, DES3state *s)
{
	int i;
	uchar tmp[8];

	for(; len >= 8; len -= 8){
		triple_block_cipher(s->expanded, p, DES3EDE);
		p += 8;
	}
	
	if(len > 0){
		for (i=0; i<8; i++)
			tmp[i] = i;
		triple_block_cipher(s->expanded, tmp, DES3EDE);
		for (i = 0; i < len; i++)
			p[i] ^= tmp[i];
	}
}

void
des3ECBdecrypt(uchar *p, int len, DES3state *s)
{
	int i;
	uchar tmp[8];

	for(; len >= 8; len -= 8){
		triple_block_cipher(s->expanded, p, DES3DED);
		p += 8;
	}
	
	if(len > 0){
		for (i=0; i<8; i++)
			tmp[i] = i;
		triple_block_cipher(s->expanded, tmp, DES3EDE);
		for (i = 0; i < len; i++)
			p[i] ^= tmp[i];
	}
}

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