Rpgp: Pure Rust implementation of OpenPGP

Project highlights & adoption

• rpgp is a pure-Rust OpenPGP implementation; some commenters report using it successfully for git commit signing with smartcards.
• Its recent HN visibility may be linked to strong conformance in the Sequoia test suite.
• The maintainer is active in the thread and open to feedback and questions.

Smartcards and integration

• rpgp doesn’t have built-in smartcard support but can integrate with external tooling.
• A proof-of-concept shows it working with OpenPGP smartcards (YubiKey, Nitrokey) for signing and decryption.
• Integration relies on the Rust pcsc crate, which uses system PC/SC libraries (Windows/macOS system libs, pcsclite on Linux).

Cryptographic design & security concerns

• SHA‑1 use in OpenPGP is debated. One view sees little urgent need to change the standard; another is adding Git-style SHA‑1 collision detection to rpgp for extra protection.
• A suspected RSA vulnerability (Desmedt–Odlyzko) was raised, then retracted after closer reading; the code in question affects signature padding but not in the initially claimed way.
• rpgp currently depends on an RSA implementation flagged for timing side channels.
  • One side argues serious primitives like RSA/AES should be implemented in assembly for robust constant-time behavior.
  • Others counter that Rust is not “too high-level” for crypto and note that even OpenSSL had similar issues; also, CPU differences limit what assembly can guarantee.

GnuPG, libraries, and ecosystem pain

• Several comments criticize GnuPG’s historical “CLI-first” design and the difficulty of using it as a library (process management, poor performance at scale, awkward key handling).
• gpgme partly mitigates this by wrapping the gpg binary, but still inherits performance and edge-case issues.
• Some see GPG as effectively legacy and fundamentally hard to fix without breaking compatibility.

Sequoia vs. rpgp & licensing

• Sequoia aims to be a full GnuPG replacement with a larger, more complex stack and has institutional funding.
• rpgp is described as smaller, more flexible, and more “Rust-native” (simple cargo add pgp experience), but with sparser docs that often require reading source.
• Licensing is a concern: some prefer MPL-style licensing over LGPL for easier integration; Sequoia’s alignment with GPL-family licenses is seen as a barrier.

OpenPGP / LibrePGP schism & cipher modes

• GnuPG has started preferring LibrePGP-specific OCB-based AEAD, causing interoperability issues with other implementations.
• Some distributions patch GnuPG defaults to avoid this.
• rpgp is adding support to read these formats for compatibility but intends to emit the most broadly compatible formats by default.
• One view holds there’s no urgent cryptographic need for new block modes, so the divergence mostly harms interoperability.

PGP vs modern messaging (Signal/WhatsApp, email substrate)

• Multiple comments contrast GPG/PGP’s poor UX and “toolbox-itis” with Signal/WhatsApp’s seamless E2EE and automatic key management.
• Email is described as a bad substrate for modern E2EE: archival expectations, metadata exposure, and retrofitting constraints all complicate things.
• Some argue that central key directories and mandatory encryption in messaging apps sidestep PGP’s hardest problems (decentralized identity, opt-in encryption).
• Others are skeptical of Signal/WhatsApp due to centralization, proprietary clients, possible platform backdoors, and SIM-based account takeover; they argue PGP remains more trustworthy under some threat models.
• There is debate over protection against state actors:
  • One side stresses that OS or device compromise breaks any app, and mainstream desktops may be easier targets than phones.
  • Another emphasizes that mobile platforms, phone numbers, and opaque components (like baseband) weaken security, especially for high-end threats.

General ecosystem reflections

• Some lament that a decent OpenPGP library ecosystem arrived only after GPG’s dominance and design choices had already “poisoned the well.”
• There is interest in higher-level, misuse-resistant APIs atop both rpgp and Sequoia, to avoid low-level types and complexity.
• Overall sentiment: rpgp is welcomed as a modern, pure-Rust alternative, but concerns remain about crypto hardening, interoperability, and the broader viability of OpenPGP for new applications.