# Tag Info

## New answers tagged key-exchange

1

I don't know the protocol, so I'm not sure. It is a standard way of converting group elements (e.g. the shared value $g^{ab}$ you get after Diffie-Hellman) to keys. You don't need to worry about the specifics of the group when choosing a hash function, just use a cryptographic hash like SHA256. It's hard to know what the difference between those two is ...

3

Any shared secret can be used. Securely distributed passwords and symmetric keys, for example. Alternatively, you can use asymmetric cryptography, such as public keys. For one example, SSH has for years authenticated servers using public key cryptography and users typically using either public keys or passwords. Only recently had SSH added support for ...

0

How they work Public and private keys work as follows. Every party who wants to communicate with others generates a private key which they keep secret. From that private key, they derive a public key, which they publish for anyone to see. For example, if we have three agents, Alice, Bob, and Charlie, they will all have a secret key S_A, S_B, and S_C and a ...

1

Elliptic curve security relies on the hardness of discrete logarithm on that curve. (Well, that's a simplification, but this will do for this answer.) When the curve contains N points, it takes an effort of roughly sqrt(N) "elementary operations" to break discrete logarithm. A prime p of "k bits" means that p is less than 2k, but greater than 2k-1. The ...

0

The [very] simplified answer is that one of the parameters for an elliptic curve is a prime p, the addition and multiplication in your elliptic curve is done (mod p), so the larger your p, the larger the set of integers you're working with, the more guesses an attacker has to make to break your key. For example, if your prime was 3, then the only possible ...

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