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Apr
16
comment Key space vs Cardinality of 1024-bit RSA
Actually, the keyspace would be the set of prime pairs between $2^{511}$ and $2^{512}$. Actually, it's somewhat less, because we insist that the product be between $2^{1023}$ and $2^{1024}$. The set of prime pairs between $2^{511.5}$ and $2^{512}$ is one way to evaluate it.
Apr
16
comment Key space vs Cardinality of 1024-bit RSA
Actually, for 1024-bit RSA, the primes generated will typically be 512 bits each...
Apr
16
comment Are keys generated by the user or block cipher algorithms themselves?
How key generation is done is a very broad topic; there are lots of ways it can be done, and as far as the block cipher algorithm is concerned, it's done by someone else.
Apr
16
reviewed Close Are keys generated by the user or block cipher algorithms themselves?
Apr
16
reviewed Close Finding Vignere Cipher key
Apr
16
reviewed Leave Open why are both ipad and opad required for HMAC?
Apr
16
reviewed No Action Needed How do I control an access code safely?
Apr
16
reviewed No Action Needed EC based password authenticated key exchange protocol
Apr
16
reviewed No Action Needed Does it make sense to have multiple values of authentication and cipher offsets while encrypting a packet?
Apr
16
answered dh parameters someone else generated
Apr
16
comment Diffie-Hellman: choosing wrong generator “g” parameter and its implications of practical attacks
Actually, I would have to disagree that, as long as you pick your DH values randomly, you're probably safe. If your value $g$ has an order $n$ with a small factor $q$, then the attacker can compute the secret exponents modulo $q$. If you pick $g$ and $p$ totally at random, there's a nonnegliable probability that $n$ will have a number of small factors; and hence you'll leak a nontrivial part of the secret. Yes, if you make the secret exponents larger to compensate -- you have to know to do so.
Apr
16
comment Choosing finite field size in Shamir's Secret Sharing Scheme
@VadymFedyukovych: it's not at all clear how good you could make it. Apart from the issues for leaking lsbits (e.g. if you have shares for 3 and 26, I believe that might leak the secret modulo 26-3=23, as 23 is uninvertible in the integers, you also have the problem of probability distributions. You must pick coefficents according to some nonuniform distribution; with $t-1$ shares, the attacker can compute, for any possible secret value, the coefficients that would have been. If any of the coefficents have probabilities that are too small, the attacker can eliminate that possibility.
Apr
16
comment Why perfect secrecy can be ensured when a plain message and a cipher-text based on one-time pad are correlated?
@zhu: if you think there might be a correlation, you might find it fruitful to select a probability distribution for $M$, and compute the resulting distribution of $M \oplus K$ (assuming an independent $K$)
Apr
16
revised Why perfect secrecy can be ensured when a plain message and a cipher-text based on one-time pad are correlated?
added 412 characters in body
Apr
16
answered Why perfect secrecy can be ensured when a plain message and a cipher-text based on one-time pad are correlated?
Apr
15
reviewed No Action Needed RFID Protocol Cryptanalysis
Apr
15
reviewed No Action Needed Asymmetric encryption that is secure for (almost) any foreseeable future
Apr
15
reviewed No Action Needed What does L_n is the bit length of the group order n states need for my calculation in ECDSA algorithm?
Apr
14
comment Choosing finite field size in Shamir's Secret Sharing Scheme
Actually, if $p=251$, then you can't fit an 8 bit value there; there are only 251 possible secret values, and hence there are 5 possible values of $S_i$ that cannot be shared.
Apr
14
answered Choosing finite field size in Shamir's Secret Sharing Scheme