RSA-PSS(7ossl)

💅 RSA-PSS — aka RSA-PSS(7ossl) from the OpenSSL manuals 🎀

okay so bestie, this is a page from the OpenSSL manual set, and it's literally all about RSA-PSS. grab a strawberry drink 🍓 and let's get into it.

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✨ NAME ✨

RSA-PSS — the EVP_PKEY RSA-PSS algorithm support, and yes it's exactly as iconic as it sounds 👑

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🌸 SYNOPSIS 🌸

sksksk there's no synopsis section here bestie, this page is pure vibes and explanation, no cap. moving on 💅

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🦋 DESCRIPTION 🦋

so the RSA-PSS EVP_PKEY implementation is basically a restricted version of the RSA algorithm. like, RSA but with a curfew 💀 it only supports:

• signing
• verification
• key generation

…and all of that only with PSS padding modes, with optional parameter restrictions on top. periodt.

it also has its own associated private key and public key formats, iykyk 🫶

this algorithm shares several control operations with the plain RSA algorithm, but with some restrictions described below. so like, same friend group, different boundaries 😭

🔥 Signing and Verification 🔥

signing and verification work similar to the RSA algorithm — except the padding mode is always PSS. no switching, no exceptions, it's giving main character energy only 🌈

and here's the cute part: if the key in use has parameter restrictions, then the corresponding signature parameters get set to those restrictions. for example — and this example is iconic so pay attention bestie 👀 — if the key can only be used with digest SHA256, MGF1 SHA256 and minimum salt length 32, then the digest, MGF1 digest and salt length will be set to SHA256, SHA256 and 32 respectively. literally matching, matching, matching ✨

🎀 Key Generation 🎀

by default, no parameter restrictions are placed on the generated key. free spirit key, no rules, living its best life 🦋

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💜 NOTES 💜

the public key format is documented in RFC4055. go read it, it's important, ngl 📖

the PKCS#8 private key format used for RSA-PSS keys is similar to the RSA format — except it uses the id-RSASSA-PSS OID, and the parameters field (if present) restricts the key parameters in the same way as the public key. same energy, different OID, you get it 💅

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👑 CONFORMING TO 👑

RFC 4055 — that's the one, that's the standard, slay 🏆

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🌟 SEE ALSO 🌟

so many little function besties to visit, go say hi to all of them:

• EVP_PKEY_CTX_set_rsa_pss_keygen_md(3)
• EVP_PKEY_CTX_set_rsa_pss_keygen_mgf1_md(3)
• EVP_PKEY_CTX_set_rsa_pss_keygen_saltlen(3)
• EVP_PKEY_CTX_new(3)
• EVP_PKEY_CTX_ctrl_str(3)
• EVP_PKEY_derive(3)

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💖 COPYRIGHT 💖

Copyright 2017-2018 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>.

⚠️ heads up bestie: that license bit is not optional. it's a real legal thing, not a vibe. read it fr fr 🙈

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okay and finally, the little sign-off corner 🎀✨ this page is from OpenSSL 3.5.6, dated 2026-04-07, and it's RSA-PSS(7ossl) — that's the whole page, you ate it, go forth and sign things with PSS padding, mwah 💋🫶💜