Getting error padding is invalid and cannot be removed while decryption

[h2007]

I am using following code to encrypt and decrypt the password,


public static string EncryptStringPassword(string plainSourceStringToEncrypt)
{
//Set up the encryption objects
using (AesCryptoServiceProvider acsp = GetProvider(Encoding.Default.GetBytes(Key)))
{
byte[] sourceBytes = Encoding.ASCII.GetBytes(plainSourceStringToEncrypt);
ICryptoTransform ictE = acsp.CreateEncryptor();

//Set up stream to contain the encryption
MemoryStream msS = new MemoryStream();

//Perform the encrpytion, storing output into the stream
CryptoStream csS = new CryptoStream(msS, ictE, CryptoStreamMode.Write);
csS.Write(sourceBytes, 0, sourceBytes.Length);
csS.FlushFinalBlock();

//sourceBytes are now encrypted as an array of secure bytes
byte[] encryptedBytes = msS.ToArray(); //.ToArray() is important, don't mess with the buffer

//return the encrypted bytes as a BASE64 encoded string
return Convert.ToBase64String(encryptedBytes);
}
}

//AES
public static string DecryptStringPassword(string base64StringToDecrypt)
{
//Set up the encryption objects
using (AesCryptoServiceProvider acsp = GetProvider(Encoding.Default.GetBytes(Key)))
{
byte[] RawBytes = Convert.FromBase64String(base64StringToDecrypt);
ICryptoTransform ictD = acsp.CreateDecryptor();

//RawBytes now contains original byte array, still in Encrypted state

//Decrypt into stream
MemoryStream msD = new MemoryStream(RawBytes, 0, RawBytes.Length);
CryptoStream csD = new CryptoStream(msD, ictD, CryptoStreamMode.Read);
//csD now contains original byte array, fully decrypted

//return the content of msD as a regular string
return (new StreamReader(csD)).ReadToEnd();
}
}

private static AesCryptoServiceProvider GetProvider(byte[] key)
{
AesCryptoServiceProvider result = new AesCryptoServiceProvider();
result.BlockSize = 128;
result.KeySize = 128;
result.Mode = CipherMode.CBC;
result.Padding = PaddingMode.PKCS7;

result.GenerateIV();
result.IV = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

byte[] RealKey = GetKey(key, result);
result.Key = RealKey;
// result.IV = RealKey;
return result;
}


Suddenly while verifying one of the users password, I am getting error "padding is invalid and can not be removed".

for other users it working fine. Only for one user its giving problem.

Will it be possible if password has been changed recently and whether it contains any particular character? or will length of the password can produce this error? Will it be because of password itself (as i said may be length or something)

(before same user has no problem signing in the app)

otherwise what can be reason for getting above error?


h2007

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