New answers tagged 3des
GCM can be defined with 64-bit ciphers, see Appendix A of here: http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/proposedmodes/gcm/gcm-spec.pdf NISTs's final GCM spec doesn't include this option. I suspect that this is because the security of GCM's MAC component depends on the difference between the number of blocks in the longest possible message and ...
According to Wikipedia, GCM is defined for block ciphers with a block size of 128 bits. So no, you can't use GCM with 3DES or DES, because of the 64-bit block size. You could use something similar to GCM, but it wouldn't be GCM.
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