RSA/ECB/OAEPWithSHA-1AndMGF1Padding 类似工具类代码

最新推荐文章于 2025-09-15 20:33:04 发布

原创

最新推荐文章于 2025-09-15 20:33:04 发布 · 3.2k 阅读

2 ·

CC 4.0 BY-SA版权

文章标签：

#加密解密

本文介绍了一种掩模生成函数MGF1的Java实现，并详细展示了使用MGF1与SHA-1进行OAEP填充的具体过程。该实现包括加密和解密两部分，适用于不同长度的消息和标签。

源码

MGF1

import java.security.MessageDigest;

/**
 * 掩模生成函数
 * mask generator function, as described in PKCS1v2.
 */
public class MGF1
{
    private MessageDigest digest;

    /**
     * Create a version of MGF1 for the given digest.
     *
     * @param digest
     *            digest to use as the basis of the function.
     */
    public MGF1(MessageDigest digest)
    {
        this.digest = digest;
    }

    /**
     * int to octet string.
     */
    private void I2OSP(int i, byte[] sp)
    {
        sp[0] = (byte) (i >>> 24);
        sp[1] = (byte) (i >>> 16);
        sp[2] = (byte) (i >>> 8);
        sp[3] = (byte) (i >>> 0);
    }

    /**
     * Generate the mask.
     *
     * @param seed
     *            source of input bytes for initial digest state
     * @param length
     *            length of mask to generate
     *
     * @return a byte array containing a MGF1 generated mask
     */
    public byte[]
    generateMask(byte[] seed, int length)
    {
        byte[] mask = new byte[length];
        byte[] C = new byte[4];
        int counter = 0;
        int hLen = digest.getDigestLength();
        digest.reset();
        while (counter < (length / hLen))
        {
            I2OSP(counter, C);
            digest.update(seed);
            digest.update(C);//update 就是把之前的跟现在的连接在一起
            System.arraycopy(digest.digest(), 0, mask, counter * hLen, hLen);

            counter++;
        }
        if ((counter * hLen) < length)
        {
            I2OSP(counter, C);
            digest.update(s