From: miron@extropia.wimsey.com (Miron Cuperman)
Date: Thu, 27 May 93 14:31:49 PDT
To: cypherpunks@toad.com
Subject: Interim patch for ytalk
Message-ID: <199305272044.AA05646@xtropia>
MIME-Version: 1.0
Content-Type: text/plain


I also intend to change the name of the program to PGTalk.  If anybody
has better ideas, please let me know.

This patch is important for the security of the encryption.  The
idea was to have cipher feedback (pun intended!).  Somehow I reversed
a couple of lines.

*** ytalk/idea.c	Thu May 27 13:40:36 1993
--- pgtalk/idea.c	Thu May 27 13:40:52 1993
***************
*** 504,510 ****
  	{
  		idea_ecb(iv,temp, Z);  /* encrypt iv_idea, making temp. */ 
  
! 		if (!decrypt)	/* buf is ciphertext */
  			/* shift in ciphertext to IV... */
  			cfbshift((byte *)iv,buf,chunksize,IDEABLOCKSIZE);
  
--- 504,510 ----
  	{
  		idea_ecb(iv,temp, Z);  /* encrypt iv_idea, making temp. */ 
  
! 		if (decrypt)	/* buf is ciphertext */
  			/* shift in ciphertext to IV... */
  			cfbshift((byte *)iv,buf,chunksize,IDEABLOCKSIZE);
  
***************
*** 511,517 ****
  		/* convert buf via xor */
  		xorbuf(buf,(byte *)temp,chunksize); /* buf now has enciphered output */
  
! 		if (decrypt)	/* buf was plaintext, is now ciphertext */
  			/* shift in ciphertext to IV... */
  			cfbshift((byte *)iv,buf,chunksize,IDEABLOCKSIZE);
  
--- 511,517 ----
  		/* convert buf via xor */
  		xorbuf(buf,(byte *)temp,chunksize); /* buf now has enciphered output */
  
! 		if (!decrypt)	/* buf was plaintext, is now ciphertext */
  			/* shift in ciphertext to IV... */
  			cfbshift((byte *)iv,buf,chunksize,IDEABLOCKSIZE);