BadPaddingException in Android encrypt

Question

I am making an Android application and I want to encrypt a String before sending it to a DataBase, and encrytpion is correct. The problem happens when decrypting the String beca

Answer 1

For those who wish to use String and Base64-encoding for usage with a database you can use these (slightly rewritten) functions from Mike Keskinov (and xalien on Anddev.org).

public String encrypt(String str) 
{
    try {

        // Encode the string into bytes using utf-8
        byte[] utf8 = str.getBytes("UTF8");

        // Encrypt
        byte[] enc = ecipher.doFinal(utf8);

        // Encode bytes to base64 to get a string 
        return new String(Base64.encode(enc,0));

    } catch (BadPaddingException e) {
    } catch (IllegalBlockSizeException e) {
    } catch (UnsupportedEncodingException e) {       
    }
    return null;
}

public String decrypt(String str) 
{
    try {

        // Decode base64 to get bytes           
        byte[] dec = Base64.decode(str, 0);

        // Decrypt
        byte[] utf8 = dcipher.doFinal(dec);

        // Decode using utf-8
        return new String(utf8, "UTF8");

    } catch (BadPaddingException e) {
    } catch (IllegalBlockSizeException e) {
    } catch (UnsupportedEncodingException e) {       
    }
    return null;
}

This code also uses the built-in Android Base64 libraries, so no need for importing any additional external libraries.

Something I didn't realise at first was how to actually use this class from another class (my ignorance). Here's a simple example:

StringEncrypter se = new StringEncrypter("mypass");
String decryptedString = se.decrypt(encryptedString);

One more thing on Base64. I found out the hard way that Base64 encoding adds a '/n' linefeed character (0x0a) whenever the string gets longer than 76 characters. This severely messes up the decrypt results. To strip out these newline characters you can add something like:

b64_enc_str = se.encrypt(plaintext_str);
str = b64_enc_str.replace("/n","");

Hopefully it helps someone.