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I am a math/computer nerd. Nothing to see here, move along.


Sep
30
awarded  Enlightened
Sep
30
awarded  Nice Answer
Sep
29
reviewed Close Is One Time Pad something like this?
Sep
29
reviewed Close Cipher built from GPU primitives
Sep
29
reviewed Close Question about second preimage resistance of hash function combiner
Sep
29
reviewed Close Hash function and indifferentiability
Sep
26
reviewed No Action Needed Determining average number of hash calls to get a hash that begins with X
Sep
24
reviewed Close stream cipher computation cost
Sep
24
revised Basic question about design of program with data encryption
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Sep
24
answered Basic question about design of program with data encryption
Sep
24
awarded  Autobiographer
Sep
20
reviewed Excellent Combining two keys
Sep
20
reviewed Excellent Elliptic Curve Cryptography
Sep
20
reviewed Excellent The REACT transform and Replayable CCA
Sep
20
reviewed Excellent Point addition equation in projective co ordinates
Sep
20
reviewed Satisfactory Is SRP post-quantum secure?
Sep
20
reviewed Satisfactory Can you fake messages from recorded message-history?
Sep
20
reviewed Satisfactory Secure MultiParty Computation with secret inputs for secret outputs
Sep
19
comment Authenticating Very Short (Sub-Block) Data
Addendum: I should probably also note that this approach won't protect you against replay attacks. While this is true of authenticated encryption in general, it's a harder problem to solve if messages are too short to include a monotonically increasing counter or some other protocol-level countermeasure. Without knowing more context, it's hard to know what threats you should be concerned with.
Sep
19
comment Authenticating Very Short (Sub-Block) Data
Length-preserving schemes are by definition FPE. But if bandwidth is an issue, you can get very short authenticated ciphertexts by using encode-then-encipher (seclab.cs.ucdavis.edu/papers/Rogaway/encode.pdf). If you pad your 64-bit payload with 0s until it's 128 bits long and encrypt using AES (in ECB mode, no IV), then you can check authenticity by verifying that the padding is all 0s when you decrypt. Some warnings: (1) an attacker will be able to learn if a message is repeated (2) this only works if messages are significantly shorter than the AES block length (128 bits).