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Nov
17
reviewed No Action Needed Show CBC-MAC construction isn't secure
Nov
17
reviewed No Action Needed what does rsaSha512Sign do?
Nov
17
reviewed Leave Open RSA with PKCS#7 and DES-EDE3-CBC (and padding)
Nov
17
reviewed Leave Open Handbook of Applied Cryptography as an entry point - is it ok book?
Nov
16
comment Checking both Quadratic residuosity and Jacobi symbol simultaneously and efficiently
Yes, our answers are pretty close; we both provide ways to do it, given a little bit of help from the key generator. With you, the help is an example value of $s$; with mine, it's asking him to ensure $p \equiv q \equiv 3 \bmod 4$ (and with that, we can find a value of $s$ ourselves)
Nov
16
reviewed No Action Needed Why is Poly1305 popular given its 'sudden death' properties?
Nov
16
reviewed No Action Needed Why sorting is needed for Meet-in-the-middle attack
Nov
16
reviewed No Action Needed Secure symmetric encryption algorithm for any-size base62 data
Nov
16
reviewed No Action Needed Decrypting A Cipher Text without knowing the key or plaintext
Nov
16
reviewed No Action Needed Block cipher to encrypt 8 bytes/64 bits - Use 64 or 128 bit cipher?
Nov
16
reviewed No Action Needed fully homomorphic encryption (FHE)
Nov
16
reviewed No Action Needed Block cipher to encrypt 8 bytes/64 bits - Use 64 or 128 bit cipher?
Nov
16
comment Why sorting is needed for Meet-in-the-middle attack
@IlmariKaronen: Minor note: we can do rather better than $O(n \log n)$ comparisons (!); the data we're sorting on is uniformly distributed, and for data like that, approaches such as radix sorting have better asymptotic complexity.
Nov
16
answered Checking both Quadratic residuosity and Jacobi symbol simultaneously and efficiently
Nov
15
comment Complexity to find an preimage of a hash function
Because they said $E_{m_i}()$ denoted the encryption of an ideal block cipher; block ciphers are, by definition, invertable. What MD hashes use in practice is $H_i = H_{i-1} \oplus E_{m_i}(H_{i-1})$; xoring in $H_{i-1}$ prevents invertibility
Nov
14
reviewed Looks OK Why we can't implement AES 512 key size?
Nov
14
comment Complexity to find an preimage of a hash function
Yes, that is what I (and the lecturer) are saying.
Nov
14
comment Complexity to find an preimage of a hash function
One note: while the lecturer was correct as regards to a Merke-Daamgard hash function with an inverible compression function, however all real MD hash functions (SHA-1, SHA-2) use a noninvertible compression function. What the lecturer was likely trying to point out why this is the case; why a compression function that is invertible is a bad idea.
Nov
14
comment Consequences of AES without any one of its operations
Yup, except for one glitch; the cipher is affine rather than linear (hence, there's this constant c sitting in the relationship); this is actually pretty easy to workaround; one way is adding an extra implied bit to each plaintext/ciphertext, which is set on every plaintext/ciphertext you have, and solve it as a set of GF(2) linear equations over 129 variables.
Nov
14
comment Consequences of AES without any one of its operations
Suppose you knew the plaintexts the correspond to the ciphertexts 1000...00, 0100...00, 0010...00, ..., 0000...001, and finally 0000...00 (all zeros). How could you use that to decrypt an arbitrary ciphertext? Extra credit question: how could you use that technique if you were given 129+ random plaintext/ciphertext pairs?