EVP_SIGNATURE-RSA(7SSL)

📦
version 4.0.3 · 13 versions
, in ubuntu stonking

💖 EVP_SIGNATURE-RSA 💖

okay bestie, welcome to the 7SSL corner of the OpenSSL manpages — this one is literally all about the EVP_PKEY RSA signature implementation ✨. No cap, if you're out here signing or verifying stuff with RSA, you're in the right place 🫶.

✨ NAME ✨

EVP_SIGNATURE-RSA — the EVP_PKEY RSA signature implementation 💅

🌸 DESCRIPTION 🌸

It's got full support for computing RSA signatures, periodt. And if you also need the tea on RSA keys themselves (not just the signing part), go read EVP_PKEY-RSA(7) 🌈.

🦋 Algorithm Names 🦋

So in this list, the names are grouped together to show that they're the same algorithm wearing multiple name tags — like one queen, many outfits 👑. And yes, the OID is in there too in canonical decimal form, which basically means you can fetch them if all you've got is a bare OID that came out looking like this after a call to OBJ_obj2txt(3) 🌟.

Not me being the one algorithm that absolutely cannot be used with EVP_PKEY_sign_message_init(3) 😭 it just can't, okay?
  • "RSA-RIPEMD160", "ripemd160WithRSA", "1.3.36.3.3.1.2"
  • "RSA-SHA2-256", "RSA-SHA256", "sha256WithRSAEncryption", "1.2.840.113549.1.1.11"
  • "RSA-SHA2-384", "RSA-SHA384", "sha384WithRSAEncryption", "1.2.840.113549.1.1.12"
  • "RSA-SHA2-512", "RSA-SHA512", "sha512WithRSAEncryption", "1.2.840.113549.1.1.13"
  • "RSA-SHA2-224", "RSA-SHA224", "sha224WithRSAEncryption", "1.2.840.113549.1.1.14"
  • "RSA-SHA2-512/224", "RSA-SHA512-224", "sha512-224WithRSAEncryption", "1.2.840.113549.1.1.15"
  • "RSA-SHA2-512/256", "RSA-SHA512-256", "sha512-256WithRSAEncryption", "1.2.840.113549.1.1.16"
  • "RSA-SHA3-224", "id-rsassa-pkcs1-v1_5-with-sha3-224", "2.16.840.1.101.3.4.3.13"
  • "RSA-SHA3-256", "id-rsassa-pkcs1-v1_5-with-sha3-256", "2.16.840.1.101.3.4.3.14"
  • "RSA-SHA3-384", "id-rsassa-pkcs1-v1_5-with-sha3-384", "2.16.840.1.101.3.4.3.15"
  • "RSA-SHA3-512", "id-rsassa-pkcs1-v1_5-with-sha3-512", "2.16.840.1.101.3.4.3.16"
  • "RSA-SM3", "sm3WithRSAEncryption", "1.2.156.10197.1.504" — these are the PKCS#1 v1.5 RSA signature schemes rocking a whole variety of message digest algorithms 💐. Every single one of them is supported when explicitly fetched with EVP_PKEY_sign_init_ex2(3) and EVP_PKEY_sign_message_init(3) 🎀. And they all come pre-set to use the pad mode "pkcs1" — and bestie, that cannot be changed 🚫.

🍓 Signature Parameters 🍓

These are the signature params you can set with EVP_PKEY_CTX_set_params(). You can call that after EVP_PKEY_sign_init() or EVP_PKEY_verify_init(), and before you call EVP_PKEY_sign() or EVP_PKEY_verify() ✨. They can also be set with EVP_PKEY_sign_init_ex() or EVP_PKEY_verify_init_ex() 💅.

  • "digest" (OSSL_SIGNATURE_PARAM_DIGEST) <UTF8 string>
  • "properties" (OSSL_SIGNATURE_PARAM_PROPERTIES) <UTF8 string>

These two? Not supported with the RSA signature schemes that already include a message digest algorithm in them — go peek at "Algorithm Names" up above, bestie 👀. These common parameters are described over in provider-signature(7) 🦋.

  • "pad-mode" (OSSL_SIGNATURE_PARAM_PAD_MODE) <UTF8 string> — this one's about the type of padding to use. Its value can be any one of these:
    • "none" (OSSL_PKEY_RSA_PAD_MODE_NONE)
    • "pkcs1" (OSSL_PKEY_RSA_PAD_MODE_PKCSV15)
    • "x931" (OSSL_PKEY_RSA_PAD_MODE_X931) — ⚠️ this padding mode is no longer supported by the FIPS provider for signature generation, but it may still be used for signature verification for legacy use cases. (It's a FIPS 140-3 requirement, iykyk 💀)
    • "pss" (OSSL_PKEY_RSA_PAD_MODE_PSS)
  • "mgf1-digest" (OSSL_SIGNATURE_PARAM_MGF1_DIGEST) <UTF8 string> — the digest algorithm name to use for the maskGenAlgorithm that "pss" mode uses 🌸.
  • "mgf1-properties" (OSSL_SIGNATURE_PARAM_MGF1_PROPERTIES) <UTF8 string> — sets the name of the property query associated with the "mgf1-digest" algorithm. NULL is used if this optional value isn't set ✨.
  • "saltlen" (OSSL_SIGNATURE_PARAM_PSS_SALTLEN) <integer> or <UTF8 string> — the "pss" mode minimum salt length. The value can be an integer, a string value representing a number, or one of these string values right here:
    • "digest" (OSSL_PKEY_RSA_PSS_SALT_LEN_DIGEST) — use the same length as the digest size.
    • "max" (OSSL_PKEY_RSA_PSS_SALT_LEN_MAX) — use the maximum salt length.
    • "auto" (OSSL_PKEY_RSA_PSS_SALT_LEN_AUTO) — auto detect the salt length.
    • "auto-digestmax" (OSSL_PKEY_RSA_PSS_SALT_LEN_AUTO_DIGEST_MAX) — auto detect the salt length when verifying, and maximize the salt length up to the digest size when signing, so you comply with FIPS 186-4 section 5.5 👑.

The OpenSSL FIPS provider also supports these parameters:

  • "key-check" (OSSL_SIGNATURE_PARAM_FIPS_KEY_CHECK) <integer>
  • "digest-check" (OSSL_SIGNATURE_PARAM_FIPS_DIGEST_CHECK) <integer>
  • "sign-x931-pad-check" (OSSL_SIGNATURE_PARAM_FIPS_SIGN_X931_PAD_CHECK) <integer>

These ones are described in provider-signature(7) — no need for me to re-spill the tea 🙈.

  • "rsa-pss-saltlen-check" (OSSL_SIGNATURE_PARAM_FIPS_RSA_PSS_SALTLEN_CHECK) <integer> — the default value of 1 causes an error during signature generation or verification if the salt length (OSSL_SIGNATURE_PARAM_PSS_SALTLEN) is not between zero and the output block size of the digest function (inclusive) 😤. Setting this to zero will ignore the error and set the approved "fips-indicator" to 0.
🚨 Heads up: this option breaks FIPS compliance if it causes the approved "fips-indicator" to return 0. Not a vibe.

The following signature parameters can be retrieved using EVP_PKEY_CTX_get_params() 🌈:

  • "algorithm-id" (OSSL_SIGNATURE_PARAM_ALGORITHM_ID) <octet string>
  • "fips-indicator" (OSSL_SIGNATURE_PARAM_FIPS_APPROVED_INDICATOR) <integer>
  • "verify-message" (OSSL_SIGNATURE_PARAM_FIPS_VERIFY_MESSAGE) <integer>

These common parameters are described in provider-signature(7) ⭐.

  • "digest" (OSSL_SIGNATURE_PARAM_DIGEST) <UTF8 string>
  • "pad-mode" (OSSL_SIGNATURE_PARAM_PAD_MODE) <UTF8 string>
  • "mgf1-digest" (OSSL_SIGNATURE_PARAM_MGF1_DIGEST) <UTF8 string>
  • "saltlen" (OSSL_SIGNATURE_PARAM_PSS_SALTLEN) <integer> or <UTF8 string>

All of these are exactly as described above, bestie 💖.

👑 SEE ALSO 👑

Copyright 2020-2026 The OpenSSL Project Authors. All Rights Reserved. 🌸

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html> ✨.

okay that's the whole page, slay 💅 this was version 4.0.3, dated 2026-09-29, and it lives under the EVP_SIGNATURE-RSA(7SSL) name — mwah, go sign something iconic bestie 🎀🦋💖

📦 where this page comes from