Sealed in Rust — Domain-Driven Edition

Cryptography is a Systems Problem

Cryptography isn’t just about math.

Yes, it starts with elegant algebra and deep number theory — but where it breaks is almost always in the system. Real-world failures come from poor implementations, leaky abstractions, memory bugs, side channels, or simply misunderstanding what problem crypto is supposed to solve.

It’s easy to misuse even “secure” primitives. AES¹ in ECB mode² is fast — and useless. RSA³ without padding⁴ is a gift to attackers. And a perfectly strong key means nothing if it’s printed to your logs.

This is why cryptography is a systems engineering problem first.

And it’s why Rust matters.

Rust doesn’t make crypto correct by default — nothing does — but it gives you tools to avoid entire classes of catastrophic bugs.

Memory safety, explicit ownership, fearless concurrency, and tight control over the machine — these aren’t “nice to have.” They’re security features.

In this book, we’ll treat crypto not as a black box, but as a series of concrete systems problems — and show how Rust lets us solve them with clarity and precision.

1. AES. Modern symmetric cipher, fast & secure. More ↩

2. ECB Mode. Simple block mode, insecure due to patterns. More ↩

3. RSA. Public-key system for encryption & signatures. More ↩

4. Padding. Adds randomness/structure to secure RSA encryption. More ↩