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Jul
11
answered In RSA, why does $p$ have to be bigger than $q$ where $n=p \times q$?
Jul
9
revised Deterministic Rand function for Winternitz One Time Signatures
added 22 characters in body
Jul
8
revised Deterministic Rand function for Winternitz One Time Signatures
added 1686 characters in body
Jul
7
revised Deterministic Rand function for Winternitz One Time Signatures
added 258 characters in body
Jul
7
asked Deterministic Rand function for Winternitz One Time Signatures
Jul
2
awarded  Curious
Jun
25
comment How come Shamir Secret Sharing uses Lagrange interpolation?
Technically, your question captures that $O(n^2) = O(kn^2 + r)$ for constant parameters $k, r$. The formula in my answer requires only about half as many multiplications, as if you were to calculate the coefficients of $P(x)$ instead of the the value of $P(0)$ directly. Newton's formula calculates the coefficients faster than Lagrange's formula, but it doesn't necessarily calculate the value of $P(0)$ faster.
Jun
25
comment How come Shamir Secret Sharing uses Lagrange interpolation?
Thanks, I improved it a bit further, to make it a bit a clearer exactly which calculations are made.
Jun
25
revised How come Shamir Secret Sharing uses Lagrange interpolation?
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Jun
24
revised How come Shamir Secret Sharing uses Lagrange interpolation?
added 403 characters in body
Jun
24
answered How come Shamir Secret Sharing uses Lagrange interpolation?
Jun
17
comment Is HMAC needed for a SHA-3 based MAC?
@figlesquidge Security is a relative notion. The question you link to in your comment, as well as the accepted answer to that question, explains in detail to what extent HMAC-SHA3 would be more secure than using in SHA3 in its built in MAC mode.
Jun
11
answered Does this protocol provide Perfect Forward Secrecy / are there potential security flaws?
May
30
comment Update to “Cryptographic Right Answers”
@otus: true, using a CA provides no advantage in case you know the server private key is compromised. However, an educated guess is that most of the time a private key is compromised the owner is blissfully unaware of the situation, which is why certificates are normally set to expire. Expiration requires a CA, in order to be handled transparently by the client software.
May
30
comment Update to “Cryptographic Right Answers”
@otus: In order to avoid having to replace all client software due to private key compromise, the client software should include the public key corresponding to the private key that stands the least risk of becoming compromised.
May
8
comment Size of p in ElGamal cryptosystem?
No, it is theoretically impossible, unless you alter either the modes or the ElGamal encryption algorithm beyond recognition. I am curious about if you had any such alterations in mind, and if you can point to a security analysis of the result.
May
8
comment Size of p in ElGamal cryptosystem?
How, and why, would you possibly use ElGamal encryption in a chaining mode? It is not a block cipher and the cipher text is always greater than the plain text.
Apr
25
comment Is the product of two primes only factorisable by those two primes?
The answer is "Yes".
Apr
21
accepted Stateless hash based public key cryptography?
Apr
21
comment Stateless hash based public key cryptography?
Indeed, thanks. Using a seeded deterministic PRF for the private keys will make it possible to recreate everything. I think it requires careful balancing of the parameters to get acceptable performance, though. Using a ten level fractal of hash trees with $2^8$ leaf nodes seems feasible.