3Des加密解密，java c#通用。

1、需要实现对其他系统的单点登陆，我们实现的方法很简单，就是将当前系统的账号通过加密去获取 需要直接登陆上的系统的token，然后访问需直接登陆的系统就带着token，就相当于登陆了。

2、然后呢，我们系统是 C#的，对方系统是Java的，对方给我们提供了 SM4的 加密。然后我这边也尝试去实现了下，发现sm4需要的 nuget包是 .net framework4.5以上版本，直接拿来用不行，然后就用dnSpy进行反编译。截取部分代码，试着不行，加密解密好像对不上，所以协商后准备两方采用新的加密方式，3Des加密，也就是多Des加密。

Des加密模式也是多种的，这边也采用了ECB，CBC，百度给出的解释是

ECB：电子密码本（最常用的，每次加密均产生独立的密文分组，并且对其他的密文分组不会产生影响，也就是相同的明文加密后产生相同的密文）。

CBC：密文链接（常用的，明文加密前需要先和前面的密文进行异或运算，也就是相同的明文加密后产生不同的密文）。

然后我在使用中得出大概的是ECB是直接密钥 加密，CBC相当于有一种加盐操作，除了密钥，还有iv。相当于CBC先是将明文做了偏移的操作，然后进行正常的3Des加密。

然后这边整理了C#版本和Java版本的3Des的加密解密的代码：

C#版本：

/// <summary>
    /// DES3加密解密
    /// </summary>
    public class Des3
    {
        #region CBC模式**
        /// <summary>
        /// DES3 CBC模式加密
        /// </summary>
        /// <param name="key">密钥</param>
        /// <param name="iv">IV</param>
        /// <param name="data">明文的byte数组</param>
        /// <returns>密文的byte数组</returns>
        public static byte[] Des3EncodeCBC(byte[] key, byte[] iv, byte[] data)
        {
            //复制于MSDN
            try
            {
                // Create a MemoryStream.
                MemoryStream mStream = new MemoryStream();
                TripleDESCryptoServiceProvider tdsp = new TripleDESCryptoServiceProvider();
                tdsp.Mode = CipherMode.CBC;             //默认值
                tdsp.Padding = PaddingMode.PKCS7;       //默认值
                // Create a CryptoStream using the MemoryStream 
                // and the passed key and initialization vector (IV).
                CryptoStream cStream = new CryptoStream(mStream,
                    tdsp.CreateEncryptor(key, iv),
                    CryptoStreamMode.Write);
                // Write the byte array to the crypto stream and flush it.
                cStream.Write(data, 0, data.Length);
                cStream.FlushFinalBlock();
                // Get an array of bytes from the 
                // MemoryStream that holds the 
                // encrypted data.
                byte[] ret = mStream.ToArray();
                // Close the streams.
                cStream.Close();
                mStream.Close();
                // Return the encrypted buffer.
                return ret;
            }
            catch (CryptographicException e)
            {
                Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
                return null;
            }
        }
        /// <summary>
        /// DES3 CBC模式解密
        /// </summary>
        /// <param name="key">密钥</param>
        /// <param name="iv">IV</param>
        /// <param name="data">密文的byte数组</param>
        /// <returns>明文的byte数组</returns>
        public static byte[] Des3DecodeCBC(byte[] key, byte[] iv, byte[] data)
        {
            try
            {
                // Create a new MemoryStream using the passed 
                // array of encrypted data.
                MemoryStream msDecrypt = new MemoryStream(data);
                TripleDESCryptoServiceProvider tdsp = new TripleDESCryptoServiceProvider();
                tdsp.Mode = CipherMode.CBC;
                tdsp.Padding = PaddingMode.PKCS7;
                // Create a CryptoStream using the MemoryStream 
                // and the passed key and initialization vector (IV).
                CryptoStream csDecrypt = new CryptoStream(msDecrypt,
                    tdsp.CreateDecryptor(key, iv),
                    CryptoStreamMode.Read);
                // Create buffer to hold the decrypted data.
                byte[] fromEncrypt = new byte[data.Length];
                // Read the decrypted data out of the crypto stream
                // and place it into the temporary buffer.
                csDecrypt.Read(fromEncrypt, 0, fromEncrypt.Length);
                //Convert the buffer into a string and return it.
                return fromEncrypt;
            }
            catch (CryptographicException e)
            {
                Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
                return null;
            }
        }
        #endregion
        #region ECB模式
        /// <summary>
        /// DES3 ECB模式加密
        /// </summary>
        /// <param name="key">密钥</param>
        /// <param name="iv">IV(当模式为ECB时，IV无用)</param>
        /// <param name="str">明文的byte数组</param>
        /// <returns>密文的byte数组</returns>
        public static byte[] Des3EncodeECB(byte[] key, byte[] iv, byte[] data)
        {
            try
            {
                // Create a MemoryStream.
                MemoryStream mStream = new MemoryStream();
                TripleDESCryptoServiceProvider tdsp = new TripleDESCryptoServiceProvider();
                tdsp.Mode = CipherMode.ECB;
                tdsp.Padding = PaddingMode.PKCS7;
                // Create a CryptoStream using the MemoryStream 
                // and the passed key and initialization vector (IV).
                CryptoStream cStream = new CryptoStream(mStream,
                    tdsp.CreateEncryptor(key, iv),
                    CryptoStreamMode.Write);
                // Write the byte array to the crypto stream and flush it.
                cStream.Write(data, 0, data.Length);
                cStream.FlushFinalBlock();
                // Get an array of bytes from the 
                // MemoryStream that holds the 
                // encrypted data.
                byte[] ret = mStream.ToArray();
                // Close the streams.
                cStream.Close();
                mStream.Close();
                // Return the encrypted buffer.
                return ret;
            }
            catch (CryptographicException e)
            {
                Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
                return null;
            }
        }
        /// <summary>
        /// DES3 ECB模式解密
        /// </summary>
        /// <param name="key">密钥</param>
        /// <param name="iv">IV(当模式为ECB时，IV无用)</param>
        /// <param name="str">密文的byte数组</param>
        /// <returns>明文的byte数组</returns>
        public static byte[] Des3DecodeECB(byte[] key, byte[] iv, byte[] data)
        {
            try
            {
                // Create a new MemoryStream using the passed 
                // array of encrypted data.
                MemoryStream msDecrypt = new MemoryStream(data);
                TripleDESCryptoServiceProvider tdsp = new TripleDESCryptoServiceProvider();
                tdsp.Mode = CipherMode.ECB;
                tdsp.Padding = PaddingMode.PKCS7;
                // Create a CryptoStream using the MemoryStream 
                // and the passed key and initialization vector (IV).
                CryptoStream csDecrypt = new CryptoStream(msDecrypt,
                    tdsp.CreateDecryptor(key, iv),
                    CryptoStreamMode.Read);
                // Create buffer to hold the decrypted data.
                byte[] fromEncrypt = new byte[data.Length];
                // Read the decrypted data out of the crypto stream
                // and place it into the temporary buffer.
                csDecrypt.Read(fromEncrypt, 0, fromEncrypt.Length);
                //Convert the buffer into a string and return it.
                return fromEncrypt;
            }
            catch (CryptographicException e)
            {
                Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
                return null;
            }
        }
        #endregion
        /// <summary>
        /// 类测试
        /// </summary>
        public static void Test()
        {
            System.Text.Encoding utf8 = System.Text.Encoding.UTF8;
            //key为abcdefghijklmnopqrstuvwx的Base64编码
            byte[] key = Convert.FromBase64String("YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4");
            byte[] iv = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };      //当模式为ECB时，IV无用
            byte[] data = utf8.GetBytes("中国ABCabc123");
            System.Console.WriteLine("ECB模式:");
            byte[] str1 = Des3.Des3EncodeECB(key, iv, data);
            byte[] str2 = Des3.Des3DecodeECB(key, iv, str1);
            System.Console.WriteLine(Convert.ToBase64String(str1));
            System.Console.WriteLine(System.Text.Encoding.UTF8.GetString(str2));
            System.Console.WriteLine();
            System.Console.WriteLine("CBC模式:");
            byte[] str3 = Des3.Des3EncodeCBC(key, iv, data);
            byte[] str4 = Des3.Des3DecodeCBC(key, iv, str3);
            System.Console.WriteLine(Convert.ToBase64String(str3));
            System.Console.WriteLine(utf8.GetString(str4));
            System.Console.WriteLine();
        }
    }

Java版本：

/**
 * @Description: TODO
 * @author: 王兵
 * @date: 2022年02月07日 9:26
 */
import java.security.Key;
import javax.crypto.Cipher;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESedeKeySpec;
import javax.crypto.spec.IvParameterSpec;
import java.util.Base64;

class Des3 {
    public static void main(String[] args) throws Exception {
        byte[] key= Base64.getDecoder().decode("YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4");
        byte[] keyiv = { 1, 2, 3, 4, 5, 6, 7, 8 };
        byte[] data="中国ABCabc123".getBytes("UTF-8");

        System.out.println("ECB加密解密");
        byte[] str3 = des3EncodeECB(key,data );
        byte[] str4 = ees3DecodeECB(key, str3);
        System.out.println(Base64.getEncoder().encodeToString(str3));
        System.out.println(new String(str4, "UTF-8"));
        System.out.println();
        System.out.println("CBC加密解密");
        byte[] str5 = des3EncodeCBC(key, keyiv, data);
        byte[] str6 = des3DecodeCBC(key, keyiv, str5);
        System.out.println(Base64.getEncoder().encodeToString(str5));
        System.out.println(new String(str6, "UTF-8"));
    }
    /**
     * ECB加密,不要IV
     * @param key 密钥
     * @param data 明文
     * @return Base64编码的密文
     * @throws Exception
     */
    public static byte[] des3EncodeECB(byte[] key, byte[] data)
            throws Exception {
        Key deskey = null;
        DESedeKeySpec spec = new DESedeKeySpec(key);
        SecretKeyFactory keyfactory = SecretKeyFactory.getInstance("desede");
        deskey = keyfactory.generateSecret(spec);
        Cipher cipher = Cipher.getInstance("desede" + "/ECB/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, deskey);
        byte[] bOut = cipher.doFinal(data);
        return bOut;
    }
    /**
     * ECB解密,不要IV
     * @param key 密钥
     * @param data Base64编码的密文
     * @return 明文
     * @throws Exception
     */
    public static byte[] ees3DecodeECB(byte[] key, byte[] data)
            throws Exception {
        Key deskey = null;
        DESedeKeySpec spec = new DESedeKeySpec(key);
        SecretKeyFactory keyfactory = SecretKeyFactory.getInstance("desede");
        deskey = keyfactory.generateSecret(spec);
        Cipher cipher = Cipher.getInstance("desede" + "/ECB/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, deskey);
        byte[] bOut = cipher.doFinal(data);
        return bOut;
    }
    /**
     * CBC加密
     * @param key 密钥
     * @param keyiv IV
     * @param data 明文
     * @return Base64编码的密文
     * @throws Exception
     */
    public static byte[] des3EncodeCBC(byte[] key, byte[] keyiv, byte[] data)
            throws Exception {
        Key deskey = null;
        DESedeKeySpec spec = new DESedeKeySpec(key);
        SecretKeyFactory keyfactory = SecretKeyFactory.getInstance("desede");
        deskey = keyfactory.generateSecret(spec);
        Cipher cipher = Cipher.getInstance("desede" + "/CBC/PKCS5Padding");
        IvParameterSpec ips = new IvParameterSpec(keyiv);
        cipher.init(Cipher.ENCRYPT_MODE, deskey, ips);
        byte[] bOut = cipher.doFinal(data);
        return bOut;
    }
    /**
     * CBC解密
     * @param key 密钥
     * @param keyiv IV
     * @param data Base64编码的密文
     * @return 明文
     * @throws Exception
     */
    public static byte[] des3DecodeCBC(byte[] key, byte[] keyiv, byte[] data)
            throws Exception {
        Key deskey = null;
        DESedeKeySpec spec = new DESedeKeySpec(key);
        SecretKeyFactory keyfactory = SecretKeyFactory.getInstance("desede");
        deskey = keyfactory.generateSecret(spec);
        Cipher cipher = Cipher.getInstance("desede" + "/CBC/PKCS5Padding");
        IvParameterSpec ips = new IvParameterSpec(keyiv);
        cipher.init(Cipher.DECRYPT_MODE, deskey, ips);
        byte[] bOut = cipher.doFinal(data);
        return bOut;
    }
}