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org.bouncycastle.crypto.engines.XSalsa20Engine Maven / Gradle / Ivy

package org.bouncycastle.crypto.engines;

import org.bouncycastle.util.Pack;

/**
 * Implementation of Daniel J. Bernstein's XSalsa20 stream cipher - Salsa20 with an extended nonce.
 * 

* XSalsa20 requires a 256 bit key, and a 192 bit nonce. */ public class XSalsa20Engine extends Salsa20Engine { public String getAlgorithmName() { return "XSalsa20"; } protected int getNonceSize() { return 24; } /** * XSalsa20 key generation: process 256 bit input key and 128 bits of the input nonce * using a core Salsa20 function without input addition to produce 256 bit working key * and use that with the remaining 64 bits of nonce to initialize a standard Salsa20 engine state. */ protected void setKey(byte[] keyBytes, byte[] ivBytes) { if (keyBytes == null) { throw new IllegalArgumentException(getAlgorithmName() + " doesn't support re-init with null key"); } if (keyBytes.length != 32) { throw new IllegalArgumentException(getAlgorithmName() + " requires a 256 bit key"); } // Set key for HSalsa20 super.setKey(keyBytes, ivBytes); // Pack next 64 bits of IV into engine state instead of counter Pack.littleEndianToInt(ivBytes, 8, engineState, 8, 2); // Process engine state to generate Salsa20 key int[] hsalsa20Out = new int[engineState.length]; salsaCore(20, engineState, hsalsa20Out); // Set new key, removing addition in last round of salsaCore engineState[1] = hsalsa20Out[0] - engineState[0]; engineState[2] = hsalsa20Out[5] - engineState[5]; engineState[3] = hsalsa20Out[10] - engineState[10]; engineState[4] = hsalsa20Out[15] - engineState[15]; engineState[11] = hsalsa20Out[6] - engineState[6]; engineState[12] = hsalsa20Out[7] - engineState[7]; engineState[13] = hsalsa20Out[8] - engineState[8]; engineState[14] = hsalsa20Out[9] - engineState[9]; // Last 64 bits of input IV Pack.littleEndianToInt(ivBytes, 16, engineState, 6, 2); } }





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