[Hardware] The market of ASICs (One GigaKey / Second?) [Repost]

[John L. Bass]

As you might note from Martin's post, this easily generates verilog with minor changes.

Have fun!
John


	Date: Sun, 8 Aug 2004 21:58:10 -0600
	From: jbass at dmsd.com
	To: hardware at lists.distributed.net
	Subject: Re: [Hardware] The market of ASICs (One GigaKey / Second?)

	Elektron <elektron_rc5 at yahoo.ca> writes:
	> Imagine loops are unrolled, since the % is incredibly wasteful. The 
	> B=L[0] line may be able to have a hard-coded value of A in some systems 
	> for a marginal speed increase (not PPC though). We don't decrypt. We 
	> encrypt the plaintext to check that it matches the ciphertext (most 
	> cores do this, and either way it's just as fast, except as mentioned, 
	> the last round is faster).

	That's pretty much what I did several years back, while trying to construct
	an FPGA based RC5 engine. The starting point was a C based code generator
	to build C and VHDL RC5 engines.

	I still having found the VHDL RC5 tools, but this is a prototype of the
	C code RC5 core generator. It still isn't perfect, but gives the C compiler
	lots of locality hints to pull all the terms into registers and discard
	the writes which can be a bottleneck on small write-thru based caches.
	Later gcc versions nearly get it perfect with -O3

	John

	/*
	 * Construct unrolled RC5 key check core
	 * John L. Bass, Copyright 2001
	 */
	main( )
	{
		const unsigned int P = 0xB7E15163;
		const unsigned int Q = 0x9E3779B9;
		
		unsigned int S[26];
		unsigned int e, i, s, l;

		/* round 0 */
		S[0]= P;
		for (s=1;s<26;s++)
			S[s]= S[s-1] + Q;
		l=0;
		printf("\t\tL%d = key0 = count;\n",l);
		printf("\t\tL%d = key1 = count>>32;\n",l+1);

		printf("\t\tS%d = ROTL3(0x%08x]);\n",
			s,S[s-26]);
		printf("\t\tL0 = ROTL(L0 + S%d, S%d);\n",
			s,s);
		s++;

		/* rounds 0,1 */
		for (;s<(2*26);s++,l^=1)
		{
			printf("\t\tS%d = ROTL3(0x%08x + S%d + %s);\n",
				s,S[s-26],s-1,l?"L1":"L0");
			printf("\t\t%s = ROTL(%s + S%d + %s, S%d + %s);\n",
				l?"L0":"L1",l?"L0":"L1",s,l?"L1":"L0",s,l?"L1":"L0");
		}

		/* rounds 2,3 */
		for (;s<(4*26);s++,l^=1)
		{
			printf("\t\tS%d = ROTL3(S%d + S%d + %s);\n",
				s,s-26,s-1,l?"L1":"L0");
			if(s != 103)
			printf("\t\t%s = ROTL(%s + S%d + %s, S%d + %s);\n",
				l?"L0":"L1",l?"L0":"L1",s,l?"L1":"L0",s,l?"L1":"L0");
			if(s == 78)
			    printf("\t\tE0 = plain0 + S%d;\n",s);
			if(s == 79)
			    printf("\t\tE1 = plain1 + S%d;\n",s);
			if(s > 79)
			printf("\t\tE%d = ROTL(E0 ^ E1, E%d) + S%d;\n",
				(s)%2,(s+1)%2,s);
		}
	}