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MGF1BytesGenerator.javaAPI DocAzureus 3.0.3.42658Tue Jun 08 05:12:58 BST 2004org.bouncycastle.crypto.generators

MGF1BytesGenerator

public class MGF1BytesGenerator extends Object implements org.bouncycastle.crypto.DerivationFunction
Generator for MGF1 as defined in PKCS 1v2

Fields Summary
private org.bouncycastle.crypto.Digest
digest
private byte[]
seed
private int
hLen
Constructors Summary
public MGF1BytesGenerator(org.bouncycastle.crypto.Digest digest)

param
digest the digest to be used as the source of generated bytes

        this.digest = digest;
        this.hLen = digest.getDigestSize();
Methods Summary
private voidItoOSP(int i, byte[] sp)
int to octet string.

        sp[0] = (byte)(i >>> 24);
        sp[1] = (byte)(i >>> 16);
        sp[2] = (byte)(i >>> 8);
        sp[3] = (byte)(i >>> 0);
public intgenerateBytes(byte[] out, int outOff, int len)
fill len bytes of the output buffer with bytes generated from the derivation function.

throws
IllegalArgumentException if the size of the request will cause an overflow.
throws
DataLengthException if the out buffer is too small.

        byte[]  hashBuf = new byte[hLen];
        byte[]  C = new byte[4];
        int     counter = 0;

        digest.reset();

        do
        {
            ItoOSP(counter, C);

            digest.update(seed, 0, seed.length);
            digest.update(C, 0, C.length);
            digest.doFinal(hashBuf, 0);

            System.arraycopy(hashBuf, 0, out, outOff + counter * hLen, hLen);
        }
        while (++counter < (len / hLen));

        if ((counter * hLen) < len)
        {
            ItoOSP(counter, C);

            digest.update(seed, 0, seed.length);
            digest.update(C, 0, C.length);
            digest.doFinal(hashBuf, 0);

            System.arraycopy(hashBuf, 0, out, outOff + counter * hLen, len - (counter * hLen));
        }

        return len;
public org.bouncycastle.crypto.DigestgetDigest()
return the underlying digest.

        return digest;
public voidinit(org.bouncycastle.crypto.DerivationParameters param)

        if (!(param instanceof MGFParameters))
        {
            throw new IllegalArgumentException("MGF parameters required for MGF1Generator");
        }

        MGFParameters   p = (MGFParameters)param;

        seed = p.getSeed();