PKCS5Padding by definition is for ciphers that have a blocksize of 8 bytes. PKCS7Padding is for blocksizes that are 1 to 255 bytes. Technically our use of PKCS5Padding is incorrect for ciphers like AES. Though PKCS5Padding has been in use forever in JCE and with very sporadic objections, it would be proper to use the correct naming convention.

The plan is to add and document by default the ciphers with PKCS7Padding naming. PKCS5Padding naming will continue to work given the long history of use and there are no plans to deprecate the naming.