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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 3 years, 6 months
seen 18 hours ago

Jul
5
comment A block cipher with independent keys for each round
@pg1989 Which only apply if you use AES with non random keys. Related key attacks are only relevant if you want to use AES in unusual ways, for example by building a hash function from it.
Jul
5
comment Is this ECC encryption key sharing method okay?
I'd prefer hashing Cx before using it as key, but that's not a big issue.
Jul
5
comment DSA, RSA, ECDSA etc - which one is cheapest for signing?
If you rotate your ECDH key only once a minute and use it for multiple connections, you need only one signature per minute. i.e. the only costly operation is ECDH. Or you can sign each time, one EC signature has half the cost of ECDH.
Jul
5
comment DSA, RSA, ECDSA etc - which one is cheapest for signing?
RSA decryption as used in RSA TLS suites authenticates. Or the DH approach CurveCP and Noise take. In either case you only prove possession of the private key to the party you're communicating with, not to everybody.
Jul
5
comment DSA, RSA, ECDSA etc - which one is cheapest for signing?
I mean that I don't like using signatures to authenticate a side in a transport security protocol, like TLS. I prefer using DH for that. DH is a bit slower, but it offers stronger deniability.
Jul
5
reviewed Approve Cryptographic Challenge: How to Say Something Confidentially to Snowden?
Jul
5
comment DSA, RSA, ECDSA etc - which one is cheapest for signing?
But I don't really like using signatures for transport encryption since it weakens deniability. I prefer EC-Diffie-Hellman, even though it's more expensive than signing.
Jul
5
comment DSA, RSA, ECDSA etc - which one is cheapest for signing?
ECDSA is rather cheap. Personally I'd go with Ed25519 for signatures, which has a easily available high performance implementations.
Jul
5
comment What is the recommended replacement for MD5?
AFAIK SHA-3 isn't specified yet, if you want to use it now you need to use a Keccak variant that'll be slightly different from the final SHA-3. So I recommend waiting until the SHA-3 standard is actually published.
Jul
5
reviewed Approve Guarding against cryptanalytic breakthroughs: combining multiple hash functions
Jul
4
comment Generate a new public/private key pair for each new message?
@Christian The problems with this one is that key management becomes annoying. That's why protocols with a live connection like SSL or OTR can use similar techniques, for example to obtain forward-secrecy. For store and forward protocols like email it's far more annoying. For example how would you support receiving mails on multiple devices?
Jul
4
comment Generate a new public/private key pair for each new message?
@Shaga It's only hard if you only consider cryptographic attacks. Attackers gaining access to the private key by compromising an endpoint is a practical threat. This includes trojans, police raids, subpoenas,...
Jul
4
reviewed Approve constructing QR-like one way function
Jul
4
comment Fast Salsa20 in java?
Do you have a link to an optimized Salsa20 implementation?
Jul
4
comment Construct a random permutation from a random function?
In the current form it's a purely theoretical problem. If this is based on a practical problem, then my impression is that your approach is misguided, i.e. that you suffer from the XY problem.
Jul
4
reviewed Approve length-extension tag wiki
Jul
4
reviewed Approve padding-oracle tag wiki excerpt
Jul
4
reviewed Approve padding-oracle tag wiki
Jul
4
reviewed Reject length-extension tag wiki
Jul
4
reviewed Reject length-extension tag wiki excerpt