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8 articles with this tag.
IPsec protects IP traffic with ESP, and IKEv2 negotiates the keys. Learn the SKEYSEED key derivation, pre-shared-key authentication, and AES-GCM, with Python code checked against 280 of NIST's own known-answer test vectors.
26 min read
OTR brings deniable, forward-secret encryption to instant messaging, with a SIGMA-style key exchange, DSA signatures, and the Socialist Millionaires' Protocol. Learn the full version 3 wire format, with Python code checked against NIST's own DSA test vectors.
27 min read
Noise is a framework for building secure channels from Diffie-Hellman exchanges. A protocol is a short pattern of tokens and a name. Learn the three state objects, the 38 handshake patterns, pre-shared keys, and the security properties, with a Python engine that reproduces 1,352 official test vectors.
34 min read
SRP is a password-authenticated key exchange. The server stores only a verifier, the password never crosses the network, and an eavesdropper cannot test guesses. Learn the SRP-6 mathematics of RFC 5054, the proofs of RFC 2945, and the checks that decide its security.
22 min read
ECDH lets two parties agree on a shared secret using points on an elliptic curve. Learn how P-256, P-384, and secp256k1 define the group, how public keys are encoded and validated, why the secret is only an x coordinate, and how an invalid-curve attack works.
23 min read
X25519 is the Diffie-Hellman function on Curve25519, defined in RFC 7748. Learn how a 32-byte private key is clamped, how the Montgomery ladder multiplies a point using only its u coordinate, why the curve was chosen, and what the all-zero check protects against.
18 min read
Diffie-Hellman's security rests on the discrete logarithm problem being hard. For a small prime, it isn't. Baby-step giant-step trades a brute-force search of size p for one of roughly √p, and that's the whole reason real DH needs huge safe primes.
11 min read
Diffie-Hellman solved cryptography's oldest problem: sharing a secret over a channel anyone can watch. Here's the math, and how it still secures the web.
14 min read
