rsa

The rsa package offers a straightforward API for basic RSA operations with minimal dependencies. Key generation, encryption/decryption, and signing work as expected with simple function calls like `rsa.encrypt()` and `rsa.sign()`. The code is readable and the examples in the documentation are clear enough to get started quickly. However, the library shows its age in several ways that impact day-to-day usage.

The pure-Python implementation means performance is significantly slower than cryptography or PyCryptodome, which becomes noticeable with larger keys or frequent operations. Error messages are often cryptic - you'll see low-level exceptions like "ValueError" without context about what went wrong with your key format or data size. Type hints are absent, making IDE support minimal and requiring constant reference to docs.

The biggest concern is the lack of modern padding schemes and key management patterns. You're responsible for choosing appropriate padding (PKCS#1 v1.5 vs OAEP), and the library doesn't guide you toward secure defaults. For production applications requiring robust cryptography, more actively maintained alternatives are safer choices.

The rsa package offers a straightforward API that's easy to grasp for basic cryptographic operations. Key generation with `rsa.newkeys()`, encryption with `rsa.encrypt()`, and signing with `rsa.sign()` work exactly as you'd expect. The documentation covers the basics adequately, and you can get a simple demo working in minutes. However, the pure-Python implementation becomes a significant limitation in real projects.

The lack of guidance around production concerns is noticeable. Error messages like 'OverflowError: X too large to encrypt' appear when your data exceeds key size limits, but the library doesn't guide you toward chunking or hybrid encryption patterns. There's minimal discussion of padding schemes (PKCS#1 v1.5 is default) or when to use OAEP. Community support is limited—GitHub issues get responses but slowly, and Stack Overflow questions often go unanswered.

Performance is the biggest practical issue. Key generation and operations are noticeably slower than cryptography.io or PyCryptodome. For educational purposes or low-throughput scenarios it works fine, but production applications will likely outgrow it quickly.

The rsa package delivers on its promise of being straightforward to use. The API is intuitive - generating keys with `rsa.newkeys(2048)`, encrypting with `rsa.encrypt()`, and signing with `rsa.sign()` works exactly as you'd expect. Documentation is minimal but sufficient for basic operations, and the examples get you started quickly. Error messages are reasonably clear when you hit size limitations or key format issues.

However, the pure-Python implementation becomes a serious constraint in real projects. Key generation is noticeably slow, and encryption operations that cryptography or pyca handle instantly can take measurable time here. You'll quickly hit the message size limitation (key_size/8 - 11 bytes), which means implementing chunking yourself for anything beyond tiny payloads. The package hasn't seen active feature development, and while it's stable, you'll find limited community support - Stack Overflow questions often redirect to cryptography library instead.

It's great for educational purposes or lightweight scripts where dependencies matter more than speed, but production applications almost always need something more robust.