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TLS Key exchange group: P-521

Percentage of IRC SSL/TLS servers with key exchange Elliptic Curve Diffie-Hellman (ECDH) using P-521 (secp521r1).
Showing percentages for charybdis servers only.

About this test result: Elliptic Curve Diffie-Hellman (ECDH) using P-521 curve (also called secp521r1).
This ECDH with classic cryptography is widely used today. However, it is not a PQC algorithm, so is vulnerable to Harvest now, decrypt later.

Table

Percentage of IRC SSL/TLS servers with key exchange Elliptic Curve Diffie-Hellman (ECDH) using P-521 (secp521r1).
Showing percentages for charybdis servers only.
Version Dec 2025
3.5 71%
4.0 100%
4.1 95%
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