decryption with rijndeal algorithm gives padding error

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hi...
i am using rijndeal to encrypt and decrypt some data! but it gives me this error :

HTML

Padding is invalid and cannot be removed.

i searched much but nothing help me to solve this error! tis is my encrypt/decrypt codes:

C#

public string Encrypt(string text)
    {

        mainRM = new System.Security.Cryptography.RijndaelManaged();
        mainRM.BlockSize = 256;
        mainRM.KeySize = 256;
        memorystream = new System.IO.MemoryStream();
        ICryptoTransform icrypt = mainRM.CreateEncryptor(key, iv);
        CryptoStream cryptstream = new CryptoStream(memorystream, icrypt, CryptoStreamMode.Write);
        cryptstream.FlushFinalBlock();
        System.IO.StreamWriter sw = new System.IO.StreamWriter(cryptstream);
        sw.Write(text);
        return Convert.ToBase64String(memorystream.ToArray());
    }

    public string Decrypt(string CryptedText)
    {
        string custinfo;
        System.IO.StreamReader streamreader;
        mainRM = new RijndaelManaged();
        mainRM.BlockSize = 256;
        mainRM.KeySize = 256;
        memorystream = new System.IO.MemoryStream(Convert.FromBase64String(CryptedText));
        ICryptoTransform icrypt = mainRM.CreateDecryptor(key, iv);
        memorystream.Position = 0;
        CryptoStream cryptstream = new CryptoStream(memorystream, icrypt, CryptoStreamMode.Read);
        cryptstream.FlushFinalBlock();
        streamreader = new System.IO.StreamReader(cryptstream);
        custinfo = streamreader.ReadToEnd();
        return custinfo;
    }

can anyone help me?

Posted 26-Apr-13 3:15am

ali_heidari_

Updated 31-Dec-19 1:00am

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Comments

StianSandberg 26-Apr-13 9:20am

Why do you modify the Blocksize and Keysize?

ali_heidari_ 26-Apr-13 9:48am

you mean, i leave Blocksize and Keysize in default value?

StianSandberg 26-Apr-13 9:52am

yes. Do you know why you modify this values?

ali_heidari_ 26-Apr-13 9:59am

this algorthm will make the data to some smaller blocks! blocksize will set lenght of this small blocks. Keysize sets size of encrypted data key value! right?

StianSandberg 26-Apr-13 10:00am

yes, but why would you change those values?

ali_heidari_ 26-Apr-13 10:06am

maybe i should not but when i try to leave them as default, my encrypted data is some freespaces, empty! when i decrypt resault is empty string! well whats your solution?

charles henington 26-Apr-13 10:21am

the iv of rijndael must be set to 16 where the key can be set to 16 or 32, have never had a reason to change the blocksize, I will provide a few encrypt and decrypt methods that will accept a password to protect the data

ali_heidari_ 26-Apr-13 10:19am

when i dnt set these, i recieve this error : Specified initialization vector (IV) does not match the block size for this algorithm.

charles henington 26-Apr-13 12:53pm

you should set the iv to 16 and the key to either 16 0r 32

public string Encrypt128(string Data, string Password)
{
byte[] clearBytes = System.Text.Encoding.Unicode.GetBytes(Data);

PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,

new byte[] { 0x00, 0x01, 0x02, 0x1C, 0x1D, 0x1E, 0x03, 0x04, 0x05, 0x0F, 0x20, 0x21, 0xAD, 0xAF, 0xA4 });
MemoryStream ms = new MemoryStream();

Rijndael alg = Rijndael.Create();
alg.Key = pdb.GetBytes(16);

alg.IV = pdb.GetBytes(16);
CryptoStream cs = new CryptoStream(ms, alg.CreateEncryptor(), CryptoStreamMode.Write);

cs.Write(clearBytes, 0, clearBytes.Length);
cs.Close();
byte[] encryptedData = ms.ToArray();
return Convert.ToBase64String(encryptedData);

}
or you could also use

public string Encrypt256(string Data, string Password)
{
byte[] clearBytes = System.Text.Encoding.Unicode.GetBytes(Data);

PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,

new byte[] { 0x00, 0x01, 0x02, 0x1C, 0x1D, 0x1E, 0x03, 0x04, 0x05, 0x0F, 0x20, 0x21, 0xAD, 0xAF, 0xA4 });
MemoryStream ms = new MemoryStream();

Rijndael alg = Rijndael.Create();
alg.Key = pdb.GetBytes(32);

alg.IV = pdb.GetBytes(16);
CryptoStream cs = new CryptoStream(ms, alg.CreateEncryptor(), CryptoStreamMode.Write);

cs.Write(clearBytes, 0, clearBytes.Length);
cs.Close();
byte[] encryptedData = ms.ToArray();
return Convert.ToBase64String(encryptedData);

}

2 solutions

Solution 2

Line 52: byte[] plainText = rijndaelCipher.CreateDecryptor().TransformFinalBlock(encryptedData, 0, encryptedData.Length);

Posted 31-Dec-19 1:00am

Member 14703898

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StianSandberg · Accepted Answer · 2013-04-26T03:18:00

Rijndael/AES is a block cypher. It encrypts data in 128 bit (16 character) blocks. Cryptographic padding is used to make sure that last block of the message is always the correct size.
You need to explicitly set the padding for both encryption and decryption.
For example:

C#

mainRM.Padding = PaddingMode.None;

Here's some code I used in a project a few months ago. It'll do the job:

C#

public static string Encrypt(string toEncrypt, string securityKey)
{
    var key = securityKey;
    var keyArray = Encoding.UTF8.GetBytes(key);

    var tdes = new TripleDESCryptoServiceProvider
    {
        Key = keyArray,
        Mode = CipherMode.ECB,
        Padding = PaddingMode.PKCS7
    };

    var cTransform = tdes.CreateEncryptor();
    var toEncryptArray = Encoding.UTF8.GetBytes(toEncrypt);
    var resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
    tdes.Clear();
    return Convert.ToBase64String(resultArray, 0, resultArray.Length);
}

public static string Decrypt(string cipherString, string securityKey)
{
    var key = securityKey;
    var keyArray = Encoding.UTF8.GetBytes(key);

    var tdes = new TripleDESCryptoServiceProvider
    {
        Key = keyArray,
        Mode = CipherMode.ECB,
        Padding = PaddingMode.PKCS7
    };

    var cTransform = tdes.CreateDecryptor();
    var toEncryptArray = Convert.FromBase64String(cipherString);
    var resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
    tdes.Clear();
    return Encoding.UTF8.GetString(resultArray);
}