I do not really like the idea to implement this padding as a new format class.
While padding could be used outside block ciphers it would be really uncommon
in my eyes. Using the format classes outside that scenario is not so uncommon.
PKCS#7 btw. is defined in
RFC 5652, which can be found here:
https://tools.ietf.org/html/rfc5652 Well that is up to you, but on side note most well known libraries do use padding classes as external implementation away from any specific implementation, example, the famous BouncyCastle
https://downloads.bouncycastle.org/j...erPadding.html
https://downloads.bouncycastle.org/j...S7Padding.html
But again, if
DEC doesn't do any padding and currently is internal for symmetric encryption then no need to expand on this, and the only missing feature to to pad to more than one block, as i explained above, this nice feature to harden the encryption by obfuscation the length, but this is up top to you to introduce.