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Aug
22
awarded  Enlightened
Aug
22
awarded  Nice Answer
Aug
20
comment Shuffleless PRNG function with non-repeating values?
search for format preserving encryption and ffx mode.
Aug
20
comment Shuffleless PRNG function with non-repeating values?
Skip32 and ipcrypt have 32 bit blocks.
Aug
19
comment File encryption with AES CTR mode
Reused kev/iv pairs amount to a many-time-pad. For many kinds of data, such as txt or html files this leaks a lot of information seeing 2 versions and nearly perfect recovery seeing 3 versions. We have several questions about that, just search a bit.
Aug
16
comment How to verify the integrity of RSA encrypted messages?
@t0b0 That an attacker can replace the key and message is always the case for asymmetric encryption. You need to add some kind of sender authentication, such as a signature or DH+MAC if you want to prevent that. The concept vlp describes is known as hybrid-encryption and sound, as long as you take the pitfalls otus mentioned into account.
Aug
14
comment Chopping off SHA256 entropy?
The only reason to prefer SipHash over truncated SHA2 is performance. SipHash isn't even designed to be collision resistant.
Aug
12
comment Security impact of signing small data using RSA
Consider using HTTPS/SSL/TLS to secure the connection in addition to your signature scheme.
Aug
12
comment Security impact of signing small data using RSA
Are you using proper padding, like PSS?
Aug
10
comment How can I compare two hash algorithms?
The best way we know for determining the security of primitives is having experts trying to break it for years. It's unlikely that they'll bother to do so with your algorithm.
Aug
10
comment Is it possible to validate a Public Key in RSA?
There are efficient algorithms with which the owner of the key can prove that e and phi(n) are co-prime.
Aug
5
reviewed No Action Needed Attribute-based encryption for cloud storage
Aug
4
comment Why do crypto libs use table lookups when they're vulnerable to timing attacks?
@user54609 bitslicing is only efficient for parallelizable modes.
Aug
2
comment Is modular Barrett reduction usable for Ed25519?
The order is still pretty close to a power-of-two, so you can use a variant of the approach described at: What are the computational benefits of primes close to the power of 2?
Jul
31
reviewed Reviewed How AES treat string input to encrypt data and what will happen if the cipher key is less than that expected?
Jul
31
revised How AES treat string input to encrypt data and what will happen if the cipher key is less than that expected?
deleted 14 characters in body; edited tags
Jul
31
comment Point addition in NaCl/libsodium (Curve25519)
It's public domain if you copy it out of NaCl or SUPERCOP.
Jul
28
comment Factorize RSA knowing several N and E
@Antimony While RSA moduli usually have two prime factors, that's not always the case. Using more factors improves the CRT speedup, but you need to be careful that the factors remain big enough so that elliptic curve factorization (whose cost depends on the size of the factors) is more expensive than GNFS (whose cost depends on the size of the modulus).
Jul
27
comment Point addition in NaCl/libsodium (Curve25519)
NaCl isn't an ECC library, it only offers higher level operations like key-exchange and signatures and doesn't have point addition in its public API. You should be able to find an edwards form point addition function in its Ed25519 implementation.
Jul
26
revised Show How to Efficiently Solve the Computational Diffie-Hellman Assumption given an Algorithm that Solves the Square-DH Problem
edited tags