On 6/24/2020 4:58 PM, Bernd Eckenfels wrote:
Hello,
JCE implements the AESWrap cipher, but it's does not offer the KWP
mode of NIST 800-38F. KW and KWP use the same wrapping algorithm W
which is also used by AESWrap, however do to different initialisation
vectors the existing implementation can not be used to implement the
padded wrapping.
Is it possible to offer KWP as a special padding mode for AESWrap or
have the W mode be it's own block mode so you can implement the
padding externally?
Gruss
Bernd
--
http://bernd.eckenfels.net
You probably know that BouncyCastle implements KWP?
Reading the comments in the AESWrapCipher code, this was created against
the XML encryption standards even though the underlying code is a
straight implementation of RFC3394.
Rather than twiddle with this current implementation and name mapping,
it may make more sense to redo this as a normal <Alg>/<mode>/<padding>
mapping. E.g. "AES/KeyWrap-NIST/NoPadding" or KWPPadding or
AutoPadding rather than the current "AESWrap". That would then allow
for "ChaCha20/KeyWrap-NIST/AutoPadding" and others.
I.e., copy the code from the current AESWrapCipher and convert it to a
mode. More work now, less later. The AutoPadding would select the no
padding if the encoded key size was a multiple of the block length, and
the KWP padding if the encoded key size was not a multiple. Or read the
IV to determine which for unwrapping.
Mike
