RSA_SIZE(3)

📦 version 4.4.0, in alpine 3.24, arch rolling

💅 RSA_SIZE — get the RSA modulus size ✨

okay so bestie, quick heads-up before we dive in: this one lives in the libcrypto library, and you're gonna need the <openssl/rsa.h> header for any of it to work. she's a classic. 💖

🌸 SYNOPSIS 🌸

#include <openssl/rsa.h>

int
RSA_size(const RSA *rsa);

int
RSA_bits(const RSA *rsa);

🎀 DESCRIPTION 🎀

so like, RSA_size() is the girl who tells you how big the RSA modulus is, in bytes. that's it, that's the job. and why do you care? because you use it to figure out how much memory you gotta allocate for an RSA encrypted value — no cap, you literally cannot skip this step. it's giving "measure twice, cut once" energy. 💅

then there's RSA_bits() which returns the number of significant bits. different unit, same icon behaviour. ✨

⚠️ important bestie!! both rsa and rsa->n must not be NULL. like, at all. not the vibe. 🫶

⭐ RETURN VALUES ⭐

the size. that's the whole answer. she gives you the size. periodt. 👑

🦋 SEE ALSO 🦋

go read the whole friend group, they all ate. 🔥

🌈 HISTORY 🌈

  • RSA_size() — first appeared in SSLeay 0.4.4, and has been available since OpenBSD 2.4. a literal ancestor, we stan a legacy icon. 👑
  • RSA_bits() — first appeared in OpenSSL 1.1.0, and has been available since OpenBSD 6.3. the younger sister who also slays. 💜

and that's the page, bestie 🎀 this one's from the Debian crew, dated June 8, 2025 — go off, you understood the assignment ✨💖

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