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Jun
27
answered Asymmetric algorithm to generate compact unique messages that can be validated
Jun
27
comment Asymmetric algorithm to generate compact unique messages that can be validated
There are smaller elliptic curves. You'll get reasonable strength for 160 bit curves, with 40 byte signatures. But a signature by itself is useless, you need a message you want to sign. To make that message unique, you might want to use a 16 byte nonce.
Jun
27
comment Asymmetric algorithm to generate compact unique messages that can be validated
If both sides have a keypair, and they know each other's public key, you could run a key-exchange algorithm to get a shared symmetric secret between these two parties. Then use that to calculate a MAC of a nonce. Assuming a 16 byte nonce and a 16 byte MAC, you get 32 bytes total. But in its plain form this will be open to replay or MitM attacks.
Jun
27
comment Asymmetric algorithm to generate compact unique messages that can be validated
Two questions: 1) Should the consumer be able to prove to third parties that the message came from the producer? 2) What about replay attacks and MiTM? | You should start in the very beginning, and describe the goals of your protocol.
Jun
27
comment Asymmetric algorithm to generate compact unique messages that can be validated
Your steps 2 and 4 are badly written. "encrypt with private key" is the case for RSA, but not most other signature algorithms. You also neglected to mention padding, which is essential for RSA signatures.
Jun
26
comment How much bigger does a precomputed lookup table get when salt is added?
You don't even need salts that large. You don't need to make creating the table infeasible, it's enough to make multi-target attacks less efficient than single target attacks. For user password-hashes, 64 bits is plenty.
Jun
26
comment How much bigger does a precomputed lookup table get when salt is added?
I don't get why you're talking about the number of users.
Jun
23
comment bcrypt - collision-resistance against chosen salt and work factor?
I'm not sure why you require collision resistance here. Shouldn't first pre-image resistance be enough?
Jun
23
revised Does it make sense to use slow hashes in digital signatures?
added 824 characters in body
Jun
23
answered Does it make sense to use slow hashes in digital signatures?
Jun
23
comment What is the difference between these AES encryption methods
I've added a comment pointing out what's wrong with that article codeproject.com/Articles/15280/…
Jun
22
comment What is the difference between these AES encryption methods
That VB article is pretty bad. Several crucial parts are plain wrong, and others are badly written and misleading. Frightning how many 5 votes it received.
Jun
21
comment Use of nonces in Kerberos and Needham–Schroeder protocols
No idea about the specific situation, but nonces are often used to prevent replay attacks.
Jun
20
comment Which blind signature schemes exist, and how do they compare?
I already know the first and third link. The second one is interesting.
Jun
20
comment Is compressing data prior to encryption necessary to reduce plaintext redundancy?
"reduces an attacker's ability to affect the decrypted output" Shouldn't the signature catch these changes, preventing the attack?
Jun
19
comment Which blind signature schemes exist, and how do they compare?
First one is the original paper for Blind RSA signatures. I can't look at the second one ATM. I hope my university has a subscription.
Jun
19
comment Are there standards for transport layer security using only symmetric keys?
If you have hardware AES, does that mean that other cryptographic functions, such as SHA1 are much slower than AES? In that case I'd consider an AES based MAC, such as CBC-MAC.
Jun
19
comment Are there standards for transport layer security using only symmetric keys?
Most SSL libraries are rather big. He'll need a specialized embedded SSL library.
Jun
19
comment Are there standards for transport layer security using only symmetric keys?
"keys actually change over time" How does that work? I don't remember anything of that kind being in non ephermal suites.
Jun
19
comment Are there standards for transport layer security using only symmetric keys?
Can you give numbers for very little flash/RAM?