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seen Mar 27 at 2:25

Working in industry as a cryptography engineer.

To contact me, email paulgrub AT umail DOT iu DOT edu


Mar
27
comment Can machine learning analyze random number generator?
You can transform a block cipher in CTR mode into a RNG using NIST's CTR_DRBG, I'm pretty sure.
Mar
9
comment Is there a format preserving cryptographically secure hash?
You could maybe derive the FPE key from a SHA256 of the plaintext... Just spitballing here, but that might work.
Mar
2
comment Is format preserving encryption suitable for use with words or names?
Interestingly, this technique can be extended to build permutations over regular languages and context-free grammars: link
Mar
2
comment Is format preserving encryption suitable for use with words or names?
Exactly. The formal name for this construction is rank-then-encipher, and was first treated in Bellare et al.'s paper on the subject: link
Jan
22
comment Diffie-Hellman on infinite groups
Just spitballing here, but part of the problem might be that sampling uniformly from an infinite set can't be done easily.
Jan
2
comment Are there cryptographic hash functions which do not have any collisions?
Not unless its range is larger than or equal to its domain. Collisions are inevitable in all other cases because of the pigeonhole principle.
Dec
8
comment Looking For Additively Homomorphic Encryption
Why can't you use hidden group order?
Dec
3
comment What cipher algorithm is this routine using?
This question appears to be off-topic because it is about a specific software implementation of cryptography.
Dec
2
comment Using the same symmetric key in both directions?
This is verifiably false. Per-direction symmetric keys prevent replay attacks.
Dec
1
comment Verifying DER encoded DSA/ECDSA signature with extra content?
Well, what does the RFC say?
Nov
14
comment As a cryptographer, what are the things I should care about in my implementation of pairing functions?
In my opinion the question is too open-ended. You should ask specific questions about specific aspects of pairing implementations. Also pairings are a new and complex primitive that are still pretty niche. Also, you could ask the author of PBC this in an email.
Nov
10
comment What is the most computationally efficient way of generating pseudo-random permutations?
FFX and the oblivious card shuffles have identical use cases. They are both used in the same way to efficiently generate PRPs for arbitrary sets.
Nov
9
comment As a cryptographer, what are the things I should care about in my implementation of pairing functions?
On number 2, can you give a citation? I know there has been work that broke the DL problem for finite fields of small characteristic, but that work doesn't apply to ECDLP.
Nov
6
comment What is the most computationally efficient way of generating pseudo-random permutations?
In terms of the number of AES calls needed to encrypt a value, it would be more expensive. For your purposes the speed difference would probably not be significant, especially if you use AES-NI.
Oct
31
comment RSA Decryption given n, e, and phi(n)
Well, do you understand how RSA encryption and decryption work?
Oct
29
comment What are SNARKs?
eprint.iacr.org/2013/879 The citations from this should get you started.
Oct
23
comment Format Preserving Encryption for 32 or 64 bit plaintext values
I seriously doubt Voltage's patent covers as much as they say it does. Anyway, for small blocks you could use any of the FPE schemes based on oblivious card shuffles, e.g. the Thorp shuffle.
Oct
23
comment Format Preserving Encryption for 32 or 64 bit plaintext values
Also, to the OP: There are plenty of other schemes which achieve FPE that are not patented. Look (for example) at the BPS mode of operation, the spec of which is on the NIST modes development page.
Oct
23
comment Format Preserving Encryption for 32 or 64 bit plaintext values
Please, for the love of god do not make custom modifications to AES when there are other solutions that could work perfectly fine.
Oct
17
comment Prove that the affine cipher over Z26 has perfect secrecy if every key is used with equal probability of 1/312
Well, I'd start by reviewing the definition of perfect secrecy.