In the following speed table, smaller numbers are better. The numbers are median single-core cycle counts on various microarchitectures. Overclocking is disabled.

The table reports cycle counts from lib25519 and, for comparison, OpenSSL and s2n-bignum. For comparability to OpenSSL's speed-testing utility, the OpenSSL cycle counts omit various OpenSSL overheads; see below for details. The s2n-bignum and lib25519 cycle counts include all overheads. There is also a lib25519+s2n line showing separate measurements of lib25519 after the optional pre-configuration ./use-s2n-bignum step.

Microarchitectures are listed in reverse chronological order of when they were introduced. Each library is assigned one foreground color in the table.

In the lib25519 distribution, command/lib25519-speed.c measures lib25519; benchmarks/*-* is the output of lib25519-speed on various machines; speedcomparison/openssl/* has code to measure OpenSSL, and measurements from various machines; speedcomparison/s2n/* has code to measure s2n-bignum, and measurements from various machines; and autogen/md-speed extracts the table from those measurements. OpenSSL benchmarks use version 3.2.1 (2024.01.30); s2n-bignum benchmarks use commit acbb18e6343f12a7944de72c1ec0991739600f8c (2024.03.18).

The table reports only median cycle counts; see the full output files for differences between multiple measurements and the median. The table reports the following major operations:

• "X key": Generating an X25519 public key and secret key. This is dh_x25519_keypair selected 32 in the lib25519-speed output (lib25519_dh_keypair in the stable API).

  For s2n-bignum, this is x25519-keygen in the s2n25519speed output, measuring the cost of curve25519_x25519base_byte_alt, or curve25519_x25519base_byte on machines where that works and is faster.

  For OpenSSL, this is x25519-keygen-main in the openssl25519speed output, measuring the cost of EVP_PKEY_Q_keygen(0,0,"X25519"). This does not include small OpenSSL overheads for converting the public key and secret key to storage format.

• "X dh": Generating an X25519 shared secret. This is dh_x25519 selected 32 in the lib25519-speed output (lib25519_dh in the stable API).

  For s2n-bignum, this is x25519-dh in the s2n25519speed output, measuring the cost of curve25519_x25519_byte_alt, or curve25519_x25519_byte on machines where that works and is faster.

  For OpenSSL, this is x25519-dh-main in the openssl25519speed output, measuring the cost of EVP_PKEY_derive (as in OpenSSL's speed-testing utility). This does not include the cost of EVP_PKEY_new_raw_public_key to decode the public key (8376 cycles on Tiger Lake), EVP_PKEY_CTX_new and EVP_PKEY_derive_init and EVP_PKEY_derive_set_peer for initialization (together 7660 cycles on Tiger Lake), and EVP_PKEY_new_raw_private_key to decode the secret key if it is not decoded already (113498 cycles on Tiger Lake).

• "X batch": Cost per secret of generating 16 separate shared secrets. This is nPbatch_montgomery25519 selected 16 in the lib25519-speed output divided by 16.

• "Ed key": Generating an Ed25519 public key and secret key. This is sign_ed25519_keypair selected 32 in the lib25519-speed output (lib25519_sign_keypair in the stable API).

  For OpenSSL, this is ed25519-keygen-main in the openssl25519speed output, measuring the cost of EVP_PKEY_Q_keygen(0,0,"ED25519"). This does not include small OpenSSL overheads for converting the public key and secret key to storage format.

• "Ed sign": Generating an Ed25519 signature of a 59-byte message. This is sign_ed25519 selected 59 in the lib25519-speed output (lib25519_sign in the stable API).

  For OpenSSL, this is ed25519-sign-main in the openssl25519speed output, measuring the cost of EVP_DigestSign (as in OpenSSL's speed-testing utility). This does not include the cost of EVP_MD_CTX_new and EVP_DigestSignInit (together 6258 cycles on Tiger Lake), and EVP_PKEY_new_raw_private_key to decode the secret key if it is not decoded already (116808 cycles on Tiger Lake).

• "Ed verif": Verifying an Ed25519 signature and recovering a 59-byte message. This is sign_ed25519_open selected 59 in the lib25519-speed output (lib25519_sign_open in the stable API).

  For OpenSSL, this is ed25519-verify-main in the openssl25519speed output, measuring the cost of EVP_DigestVerify (as in OpenSSL's speed-testing utility). This does not include the cost of EVP_MD_CTX_new and EVP_DigestVerifyInit (together 6054 cycles on Tiger Lake), and EVP_PKEY_new_raw_public_key to decode the public key being used for verification (9560 cycles on Tiger Lake).

• "Ed MSM": Cost per point of multi-scalar multiplication with 16 points and 16 full-size scalars. This is multiscalar_ed25519 selected 16 in the lib25519-speed output divided by 16.