problems with DESede/ECB/NoPadding

> I use DESede/ECB/NoPadding and my code works

> correctly. but when i put some string to encrypt that

> is not a multiple of 8, as you know, it crash.

DES and DESede require the data length to be a multiple of 8 bytes. Using DESede/ECB/NoPadding, it is your responsibility to force this condition. You could use

DESede/ECB/PKCS5Padding

and then the padding to an 8 byte boundary will be done for you.

If you need to know how PKCS5 padding works, use Google.

sabre150a at 2007-7-7 17:21:48 >

> dun forget DESede uses 112 or 168 size keys

This is a little simplistic as far as the SunJCE JCE provider is concerned.

A DES key is 56 bits and Triple DES key is either 2x56 bits or 3x56 bits. The first 56 bits

of 2x56 Bit Triple DES key is used to DES encrypt a block, the second 56 bits is used to

DES decrypt the the result of the first DES encryption and the first 56 bits is then used

again to further DES encrypt the block. A 3x56 Bit Triple DES key uses the first 56 bits to

encrypt a block, the second 56 bits to DES decrypt the result of the first DES encryption

and then finally the 3rd 56 bit key is used to DES encrypt.

Within the SunJCE provider, a DES key is packaged as 8 bytes of 7 bits with the least

significant bit of each byte being a parity bit. I can't remember whether it is even or odd

parity but it does not matter because the SunJCE provider ignores this bit!

A Triple DES key is packages as 24 bytes with the first 8 bytes bring used for the DES

key first encryption stage, the next 8 bytes as the DES key for the decryption stage and

the last 8 bytes used for the final DES encryption stage. If one tries to provide just 16

bytes as a representation of the 2x56 Bit key then one gets a

java.security.InvalidKeyException: Wrong key size

exception. If one wants the same 56 bit key used for both encryption stages of Triple

DES encryption then one must build the appropriate 24 bytes.

sabre150a at 2007-7-7 17:21:48 >