Tag
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
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
OPAQUE is a password-authenticated key exchange that gives a server nothing to steal: not the password, not a dictionary-attackable verifier. Learn the oblivious pseudorandom function at its core, the envelope that hides a client's key pair, and the 3DH handshake, with Python code that reproduces the official RFC 9807 test vectors.
30 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
SSH secures remote logins with a binary packet protocol, a curve25519-sha256 key exchange, and an Ed25519 host key. Learn the handshake and the chacha20-poly1305@openssh.com cipher, with Python code that reproduces the IETF draft's own worked example byte for byte.
29 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 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
