Cipher, Java encrypt, C# decrypt

Question

I have the following encrypt/decrypt methods on JAVA

private static final String ALGORITHM = "AES";

 protected static String encrypt(String valueToEnc, byte[] keyValue) throws Exception {
    Key key = generateKey(keyValue);
    Cipher c = Cipher.getInstance(ALGORITHM);
    c.init(Cipher.ENCRYPT_MODE, key);
    byte[] encValue = c.doFinal(valueToEnc.getBytes());
    String encryptedValue = new BASE64Encoder().encode(encValue);
    return encryptedValue;
}

protected static String decrypt(String encryptedValue, byte[] keyValue) throws Exception {
    try
    {
        Key key = generateKey(keyValue);
        Cipher c = Cipher.getInstance(ALGORITHM);
        c.init(Cipher.DECRYPT_MODE, key);
        byte[] decordedValue = new BASE64Decoder().decodeBuffer(encryptedValue);
        byte[] decValue = c.doFinal(decordedValue);
        String decryptedValue = new String(decValue);
        return decryptedValue;
    }
    catch(Exception ex)
    {
        return "";
    }
}

private static Key generateKey(byte[] keyValue) throws Exception {          
    Key key = new SecretKeySpec(keyValue, ALGORITHM);
    return key;
}

What would be the equivalent decryption for (C#).NET?. I have tested some Cipher examples that I have found, but none of them return the same as the Java Version.

Thanks.

possible duplicate? http://stackoverflow.com/questions/19698272/encrypt-in-java-and-decrypt-in-c-sharp-for-aes-256-bit — Thiago Custodio, Dec 23 '13 at 20:57
ECB is not secure. You should use CBC, and use a random unique IV. — SLaks, Dec 23 '13 at 20:58
@ThiagoCustodio, if I use the example as it is a "Invalid Character in base64" exception is thrown. — Ferite, Dec 23 '13 at 22:58

score 0 · Answer 1 · answered Dec 26 '13 at 00:42

Try this:

using System;
using System.IO;
using System.Security.Cryptography;

namespace Aes_Example
{
    class AesExample
    {
        public static void Main()
        {
            try
            {

                string original = "Here is some data to encrypt!";

                // Create a new instance of the AesCryptoServiceProvider 
                // class.  This generates a new key and initialization  
                // vector (IV). 
                using (AesCryptoServiceProvider myAes = new AesCryptoServiceProvider())
                {

                    // Encrypt the string to an array of bytes. 
                    byte[] encrypted = EncryptStringToBytes_Aes(original, myAes.Key, myAes.IV);

                    // Decrypt the bytes to a string. 
                    string roundtrip = DecryptStringFromBytes_Aes(encrypted, myAes.Key, myAes.IV);

                    //Display the original data and the decrypted data.
                    Console.WriteLine("Original:   {0}", original);
                    Console.WriteLine("Round Trip: {0}", roundtrip);
                }

            }
            catch (Exception e)
            {
                Console.WriteLine("Error: {0}", e.Message);
            }
        }
        static byte[] EncryptStringToBytes_Aes(string plainText, byte[] Key, byte[] IV)
        {
            // Check arguments. 
            if (plainText == null || plainText.Length <= 0)
                throw new ArgumentNullException("plainText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("Key");
            byte[] encrypted;
            // Create an AesCryptoServiceProvider object 
            // with the specified key and IV. 
            using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
            {
                aesAlg.Key = Key;
                aesAlg.IV = IV;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for encryption. 
                using (MemoryStream msEncrypt = new MemoryStream())
                {
                    using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    {
                        using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                        {

                            //Write all data to the stream.
                            swEncrypt.Write(plainText);
                        }
                        encrypted = msEncrypt.ToArray();
                    }
                }
            }


            // Return the encrypted bytes from the memory stream. 
            return encrypted;

        }

        static string DecryptStringFromBytes_Aes(byte[] cipherText, byte[] Key, byte[] IV)
        {
            // Check arguments. 
            if (cipherText == null || cipherText.Length <= 0)
                throw new ArgumentNullException("cipherText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("IV");

            // Declare the string used to hold 
            // the decrypted text. 
            string plaintext = null;

            // Create an AesCryptoServiceProvider object 
            // with the specified key and IV. 
            using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
            {
                aesAlg.Key = Key;
                aesAlg.IV = IV;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for decryption. 
                using (MemoryStream msDecrypt = new MemoryStream(cipherText))
                {
                    using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    {
                        using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        {

                            // Read the decrypted bytes from the decrypting stream 
                            // and place them in a string.
                            plaintext = srDecrypt.ReadToEnd();
                        }
                    }
                }

            }

            return plaintext;

        }
    }
}

source: http://msdn.microsoft.com/en-us/library/system.security.cryptography.aescryptoserviceprovider(v=vs.110).aspx

This is a good example of encrypting/decrypting, all on .NET. But I need a routine that can decrypt the strings encrypted with the JAVA code shown above. Thanks. — Ferite, Dec 27 '13 at 15:42
@Ferite pay attention to my code: // Decrypt the bytes to a string. string roundtrip = DecryptStringFromBytes_Aes(your_java_encrypted_string, myAes.Key, myAes.IV); — Thiago Custodio, Dec 27 '13 at 17:57
as the C# application is on Framework 2.0, I have to change AesCryptoServiceProvider for RijndaelManaged. When I tested the code a "Length of the data to decrypt is invalid." exception is thrown. The input encrypted string was produced from the encryption Java application. However I have to say , I have not clear how the inicialization vector should be generated (I don't see such inicialization vector equivalent in the Java code). — Ferite, Dec 27 '13 at 22:11

Cipher, Java encrypt, C# decrypt

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