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x25519

ECDHE | Security: ~128 bits | Code: 29

Group Details

Group Name
x25519
Group Code (Decimal)
29
Group Code (Hex)
0x001D
Type
ECDHE
Security Level
~128 bits

What is x25519?

X25519 (Curve25519) is the most popular elliptic curve for TLS 1.3 key exchange, offering excellent security and performance. It provides approximately 128 bits of security and is significantly faster than NIST curves like secp256r1. X25519 was designed by Daniel J. Bernstein with a focus on side-channel resistance and simplicity. Unlike NIST curves, X25519 has no known patents or back doors. Modern browsers (Chrome, Firefox, Safari, Edge) prefer X25519 over other curves. Its popularity makes it the first choice for ECDHE key exchange in TLS 1.3. X25519 is defined in RFC 7748.

Role in JA3 Fingerprinting

The x25519 group is used for ECDHE key exchange in TLS, providing perfect forward secrecy. Different browsers and HTTP clients advertise different supported groups, making this a key component of JA3 fingerprints.

Fingerprinting Impact: The order and selection of supported groups reveals browser type, version, and security preferences.

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Technical References