com.cryptoregistry.tweet.salt.pqc.Reduce Maven / Gradle / Ivy

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Built on the nucleus of TweetNaCl, TweetPepper provides contemporary key formats, key protection using SCrypt/SecretBox, digital signature support scheme featuring CubeHash, key encapsulation using Salsa20, and other useful features you probably want anyway.

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/*
 Copyright (c) 2000-2015 The Legion of the Bouncy Castle Inc. (http://www.bouncycastle.org)
 */
package com.cryptoregistry.tweet.salt.pqc;

class Reduce {
	static final int QInv = 12287; // -inverse_mod(p,2^18)
	static final int RLog = 18;
	static final int RMask = (1 << RLog) - 1;

	static short montgomery(int a) {
		int u = a * QInv;
		u &= RMask;
		u *= Params.Q;
		u += a;
		return (short) (u >>> RLog);
	}

	static short barrett(short a) {
		int t = a & 0xFFFF;
		int u = (t * 5) >>> 16;
		u *= Params.Q;
		return (short) (t - u);
	}
}