Invalid length for a Base-64 char array or string

Question

1.00/5 (2 votes)

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I have 2 class
1. crypto class
2. login window class

decryption code is:-

public string DecryptData(string encryptedtext)
      {
          byte[] encryptedBytes = Convert.FromBase64String(encryptedtext);
          MemoryStream ms = new MemoryStream();
          CryptoStream decStream = new CryptoStream(ms, tripleDESCryptoServiceProvider.CreateDecryptor(), CryptoStreamMode.Write);
          decStream.Write(encryptedBytes, 0, encryptedBytes.Length);
          decStream.FlushFinalBlock();
          return System.Text.Encoding.Unicode.GetString(ms.ToArray());
      }

Login Code :-

MessageBox.Show(Crypto.DecryptData(obj.password))

when we call decrypt method then give an exception that is Invalid length for a Base-64 char array or string

Posted 10-Feb-15 22:11pm

J{0}Y

Updated 10-Jul-19 18:35pm

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4 solutions

Solution 2

Change

C#

//byte[] encryptedBytes = Convert.FromBase64String(encryptedtext);
byte[] encryptedBytes = Encoding.ASCII.GetBytes(encryptedtext);

This will eliminate the "Invalid length" error.

Moreover: How can you decrypt without providing a key?
Please have a look here:
Encrypt and Decrypt Data with C#[^]

Posted 10-Feb-15 22:43pm

TheRealSteveJudge

Solution 5

Please replace the below function :

public string DecryptData(string encryptedtext)
{
    encryptedtext = encryptedtext.Replace(" ", "+");
    int mod4 = encryptedtext.Length % 4;
    if (mod4 > 0 )
    {
        encryptedtext += new string('=', 4 - mod4);
    }

    byte[] encryptedBytes = Convert.FromBase64String(encryptedtext);
    MemoryStream ms = new MemoryStream();
    CryptoStream decStream = new CryptoStream(ms, 
       tripleDESCryptoServiceProvider.CreateDecryptor(), CryptoStreamMode.Write);
    decStream.Write(encryptedBytes, 0, encryptedBytes.Length);
    decStream.FlushFinalBlock();
    return System.Text.Encoding.Unicode.GetString(ms.ToArray());
}

C#

Posted 10-Jul-19 18:35pm

G.M. Patel Tana

Updated 10-Jul-19 18:37pm

v3

Solution 4

byte[] b  = Convert.FromBase64String(CypherText.Replace("", "+"));

Posted 3-Jun-19 23:54pm

JIYAUL MUSTAPHA

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Kornfeld Eliyahu Peter · Accepted Answer · 2015-02-10T22:22:00

Solution 1

For a string to be a valid Base64 string, its length must have a multiple of 4...
Check your input string's length...
http://en.wikipedia.org/wiki/Base64[^]

Posted 10-Feb-15 22:22pm

Kornfeld Eliyahu Peter

Comments

J{0}Y 11-Feb-15 4:33am

how to check my input string's length

Kornfeld Eliyahu Peter 11-Feb-15 4:42am

if((encryptedtext.Length % 4) == 0) // good for Base64

J{0}Y 11-Feb-15 6:01am

http://stackoverflow.com/questions/28450852/invalid-length-for-a-base-64-char-array-or-string
check this link

Kornfeld Eliyahu Peter 11-Feb-15 6:08am

I did...What about?

J{0}Y 11-Feb-15 6:14am

actually my question

Kornfeld Eliyahu Peter 11-Feb-15 6:20am

The answer probably is that your string not base64 encoded (base64 is not an encryption!!!)...
However it is still unclear to me what do you want...

J{0}Y 11-Feb-15 6:27am

dfghfgdfgd667878nnvghv is encrypted by base64 encoded or not

Kornfeld Eliyahu Peter 11-Feb-15 6:50am

As it's length is not a multiple of 4 - not it is not

J{0}Y 11-Feb-15 7:29am

ohk thanks