B4A Library Base64 and Encryption library

Here's a library that, for the moment, can perform Base64 encoding and decoding and symmetric algorithm encryption and decryption. Tested symmetric algorithms are DES, Triple DES and AES (Rijndael).

As the Java encryption rountines are all byte array oriented you will need my ByteConverter library to run the demo.

EDIT :- Version 1.1 posted. Asymmetric algorithms, Signing and MACs now implemented. See post#2 for details.

 

[Fabrice La]

Hello
I juste used your "code module for cripting passwords"

but the text decrypted is not the same.

What I am doing wrong ....

 

[Fabrice La]

I am using your code exactly like it is.

If I use "password" as text this is the crypted part:
79E2F0264C042BDBE25FE42A54129B89

and if I decrypt it :
y??&L+??_?*T??

Not realy the same :BangHead:

 

[Fabrice La]

Nobody to answer .....:sign0163:

 

[peacemaker]

Strange. I've rechecked - it works.
Passwords are encoded before saving to a file, and decoded just after reading from this file.
I tried before with password like "111", "222"...but now have checked "pass" - it's decoded well also.

 

[Rusty]

My encryption/decryption works great within the Android environment.
Does anyone have sample VB.NET code to encrypt/decrypt data transferred (encrypted) from the Android to the PC?
If so, can you please post it?
Thanks in advance.

 

[NJDude]

Is THIS what you're looking for?

 

[Rusty]

Perfect! Exactly what I needed, Thanks!

 

[psdos]

Agraham, you library support RC4 encryption?

Thanks.

 

[agraham]

I believe that Android supports it (as ARC4) but to use it would need the CipherStream classes exposed in the library which I did not do.

 

[Rusty]

I am using your encryption library and all works well, both encrypt and decrypt.
However, if I encrypt a 5 byte text, the returned encrypted data is 24 bytes long. Likewise, if I encrypt a 10 or 12... byte it comes back 24 bytes long.
Is there a parameter or setting I'm using incorrectly that sets this length?
Thanks,

 

[agraham]

You don't show any code nor do you even tell me what algorithm you are using However it sounds more like you are calculating a hash rather than doing encryption.

 

[Rusty]

Sorry, I made too many assumptions.

Sub fnEncrypt(dataToEncrypt As String ) As String 
    Dim kg As KeyGenerator
    Dim c As Cipher
    Dim B64 As Base64
    Dim Bconv As ByteConverter

    Dim data(0) As Byte
    Dim iv(0) As Byte
    iv = Array As Byte(211, 5, 233, 24, 55, 166, 7, 88) ' 16 bytes for AES
        
    c.Initialize("DESEDE/CBC/PKCS5Padding")     '   "DESEDE/CBC/NoPadding")            '
    c.InitialisationVector = iv
    kg.Initialize("DESEDE") 
    
    kg.KeyFromBytes(Bconv.StringToBytes("1234567890123456","ASCII"))
    data = Bconv.StringToBytes(dataToEncrypt, "ASCII")        
    data = c.Encrypt(data, kg.Key, True)                

    Return B64.EncodeBtoS(data, 0, data.Length)
    
End Sub

I pass in "Mr Smith" (as an example) and the data returned is 24 bytes long, it decrypts just fine back to "Mr Smith", but I'm trying to understand why the 8 bytes converts to 24 bytes. I'm trying to then write the data into a database with a fixed length column. My column is 20 bytes long and Mr Smith would fit just fine un-encrypted.
I'm sure I've got a parameter or a padding set wrong.
Thanks for your quick response.
I just tried the DESEDE/CBC/NoPadding and the resultant string was 12 bytes long instead of 24. Is there an overhead imposed upon encrypted strings that require longer results than the original string?

 

[agraham]

DESEDE (triple-DES) is a block cipher. Data is padded (that's the PKCS5Padding bit) to a length that is a multiple of 8 bytes then each 8 byte block is encrypted in turn (that's the CBC bit) and the encrypted data will be a multiple of 8 bytes. In the case of "Mr Smith" you get 16 bytes. Your Base64 encoding then stretches each 8 byte block to 12 characters (not bytes) hence 24 characters in this case. As strings are coded as UTF16 characters in Java the string is actually 48 bytes long. However when saved to the database if probably gets re-encoded to UTF8 characters (and encoded back to UTF16 when read) which in the case of the Base64 character set will come back down to a 24 byte string in the actual database file.

 

[Rusty]

Is there an algorithm for calculating a database column width to store an encrypted string?
i.e. A 10 character string after encryption will be 24 characters
A 24 character string after encryption will be 48 characters...etc.
Thanks for the help.

 

[agraham]

Don't confuse bytes and characters, they are not synonymous as I already indicated. The numbers are in my post.

 

[Rusty]

Thanks Agraham,
My mistake in expression of bytes/characters, I know better..

 

[mddmx]

Sorry for a stupid question and I am sure that I a missing a major point

Am I supposed to provide the Encrypt and Decrypt String functions some kind of unique seed value ?

Doesn't seem secure if we are all using the same example code ?????

Thank you.


Never mind I found the answer. The following needs to be changed to a unique 16 character string
kg.KeyFromBytes(bconv.StringToBytes("1234567890123456","ASCII"))

Makes me wonder how many times this block of code was used "as is" ...... ?

 

[PFlores81]

Would it be possible to use this to do real time encryption of certain parts of the ext_sdcard ? I ask because the project I am working on requires some sort of encryption for it to be completed.

I still dont have the initial pw prompt setup for when you load the app. but encryption is more important

 

[NeoTechni]

I'm getting:
javax.crypto.IllegalBlockSizeException: data not block size aligned

On large blocks of HTML I'm encrypting for an email inbox
The text is a multiple of 16 digits in length, but once it goes through Bconv.StringToBytes it's not anymore.

 

[Erel]

You will need to pad the bytes array with zero bytes.