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implementing successive squaring algorithm

• To: mathgroup at smc.vnet.net
• Subject: [mg23218] implementing successive squaring algorithm
• From: "Matthew Herman" <Henayni at hotmail.com>
• Date: Mon, 24 Apr 2000 01:12:26 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Hi,

I was looking to implement the successive squaring algorithm (same as 
PowerMod), and I seem to have it, but the program won't store the 
modulus value.
I took apart the program to the base of the problem, if anyone has 
suggestions let me know.

pmod[a_,b_,m_]:=g[a,IntegerDigits[b,2],m];
g[a_,blist_,m_]:=blist*Reverse[NestList[f,a,(Length[blist]-1)]];
f[a_] := Mod[a^2, m]

What happens is that I get the NestList with it not being evaluated for 
m=modulus.

Thanks

matt

• Follow-Ups:
  • Re: implementing successive squaring algorithm
    • From: Hartmut Wolf <hwolf@debis.com>