org.bouncycastle.crypto.paddings.X923Padding.java Source code

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Here is the source code for org.bouncycastle.crypto.paddings.X923Padding.java

Source

package org.bouncycastle.crypto.paddings;

import java.security.SecureRandom;

import org.bouncycastle.crypto.InvalidCipherTextException;

/**
 * A padder that adds X9.23 padding to a block - if a SecureRandom is
 * passed in random padding is assumed, otherwise padding with zeros is used.
 */
public class X923Padding implements BlockCipherPadding {
    SecureRandom random = null;

    /**
     * Initialise the padder.
     *
     * @param random a SecureRandom if one is available.
     */
    public void init(SecureRandom random) throws IllegalArgumentException {
        this.random = random;
    }

    /**
     * Return the name of the algorithm the padder implements.
     *
     * @return the name of the algorithm the padder implements.
     */
    public String getPaddingName() {
        return "X9.23";
    }

    /**
     * add the pad bytes to the passed in block, returning the
     * number of bytes added.
     */
    public int addPadding(byte[] in, int inOff) {
        byte code = (byte) (in.length - inOff);

        while (inOff < in.length - 1) {
            if (random == null) {
                in[inOff] = 0;
            } else {
                in[inOff] = (byte) random.nextInt();
            }
            inOff++;
        }

        in[inOff] = code;

        return code;
    }

    /**
     * return the number of pad bytes present in the block.
     */
    public int padCount(byte[] in) throws InvalidCipherTextException {
        int count = in[in.length - 1] & 0xff;

        if (count > in.length) {
            throw new InvalidCipherTextException("pad block corrupted");
        }

        return count;
    }
}