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Apr
19
comment Exploiting XOR one-time-pads with dictionary length that isn't a power of 2
Computer based implementations almost always operate on sequences of bits/bytes which obviously are powers-of-two. Classical implementations often use modular addition.
Apr
19
comment Exploiting XOR one-time-pads with dictionary length that isn't a power of 2
How would you even implement xor over an alphabet that isn't a power-of-two?
Apr
19
reviewed Approve Are the definitions of IND-CCA secure and of IND-CCA secure under standard model identical?
Apr
19
comment How to crack unknown 8-bit encryption algorithm?
What do you mean by "8-bit encryption"? The block size?
Apr
18
comment Meaning of “random n/2 bit prime length prime p”
You need to distinguish between the modulus itself and its size.
Apr
17
comment can pdfcrack software crack a 128 bit encrypted pdf file
Depends on the password. If it's a good password it should never finish.
Apr
16
comment (How) Can we use HOTP for file encryption?
1) It only claims HOTP, not TOTP support. 2) It might hash several consecutive OTPs to form a high entropy secret. If you repeat that process with many starting points and encrypt the same master secret with all of these possible one-time-keys, (essentially forming 1 of n secret sharing) you could get something workable.
Apr
14
revised How to reverse this hash function?
deleted 386 characters in body
Apr
14
comment How to reverse this hash function?
@RaghuDixit I'm no expert, but wouldn't standard approaches like Gaussian elimination work? Just make sure that you compute the scalar operations in the finite field and not over integers/reals. In particular make sure to use modular multiplicative inverses to compute divisions.
Apr
13
comment Is OCB the state of the art in authenticated encryption modes of operation for block ciphers?
To improve the security of OCB you could use a naturally tweakable block-cipher and/or wider blocks. Threefish would be an obvious choice. But of course it can't take advantage of AES-NI.
Apr
13
comment Is OCB the state of the art in authenticated encryption modes of operation for block ciphers?
A recent paper generated such authenticated modes automatically. But those that matched OCB's features were trivially equivalent to OCB. Automated Analysis and Synthesis of Authenticated Encryption Schemes - Viet Tung Hoang and Jonathan Katz and Alex J. Malozemoff
Apr
13
answered How to reverse this hash function?
Apr
13
revised How to reverse this hash function?
edited tags
Apr
13
comment Calculating characters from the sum of ASCII pairs
Attacking this is very similar to attacking a many-time-pad. One advanced attack example: crypto.stackexchange.com/questions/59/…
Apr
13
comment Does “double RC4” exhibit the same weaknesses as standard RC4?
@MaartenBodewes I'm too lazy to figure out the details. And poncho is our RC4 expert here.
Apr
12
comment Does “double RC4” exhibit the same weaknesses as standard RC4?
The only weakness in RC4-drop-n (for sufficiently large n), I know of, are the n-gram biases. Those should become much smaller when combining two key-streams, so the amount of data you can produce before it becomes distinguishable should become much bigger.
Apr
12
awarded  Enlightened
Apr
12
awarded  Nice Answer
Apr
12
awarded  Nice Question
Apr
12
comment What's the appeal of using ChaCha20 instead of AES?
Do the ChaCha: better mobile performance with cryptography - CloudFlare blog