org.spongycastle.crypto.signers.NTRUSignerPrng Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of scprov-jdk15on Show documentation
Show all versions of scprov-jdk15on Show documentation
The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms.
This jar contains JCE provider for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.7.
package org.spongycastle.crypto.signers;
import java.nio.ByteBuffer;
import org.spongycastle.crypto.Digest;
/**
* An implementation of the deterministic pseudo-random generator in EESS section 3.7.3.1
*/
public class NTRUSignerPrng {
private int counter;
private byte[] seed;
private Digest hashAlg;
/**
* Constructs a new PRNG and seeds it with a byte array.
* @param seed a seed
* @param hashAlg the hash algorithm to use
*/
NTRUSignerPrng(byte[] seed, Digest hashAlg) {
counter = 0;
this.seed = seed;
this.hashAlg = hashAlg;
}
/**
* Returns n random bytes
* @param n number of bytes to return
* @return the next n random bytes
*/
byte[] nextBytes(int n) {
ByteBuffer buf = ByteBuffer.allocate(n);
while (buf.hasRemaining()) {
ByteBuffer cbuf = ByteBuffer.allocate(seed.length + 4);
cbuf.put(seed);
cbuf.putInt(counter);
byte[] array = cbuf.array();
byte[] hash = new byte[hashAlg.getDigestSize()];
hashAlg.update(array, 0, array.length);
hashAlg.doFinal(hash, 0);
if (buf.remaining() < hash.length)
buf.put(hash, 0, buf.remaining());
else
buf.put(hash);
counter++;
}
return buf.array();
}
}