Cryptography in .NET: Patterns & Pitfalls

Modern .NET cryptography is not about elliptic curves or cipher implementation. It is about recognizing when encryption is necessary, using battle-tested APIs correctly, and managing cryptographic keys with the paranoia they deserve. The fastest path to an audit failure is a developer who decided base64 encoding was good enough, XOR with a hardcoded byte array counts as encryption, or that compilation obscures secrets in any meaningful way.

The articles in this collection treat cryptography as a specialization rather than a feature sprint. The .NET Data Protection API is the starting point because it exists precisely to solve the problems most developers do not know they have: purpose strings that prevent ciphertext from being decrypted in the wrong context, key rotation that happens automatically on a configurable cadence, and key storage abstractions that integrate with Azure Key Vault, file system providers, and Redis without leaking implementation details into application code.

Key management gets specific attention because it is where most production cryptography fails. Keys stored in appsettings.json, environment variables checked into the repository, certificates that expired six months ago in a forgotten Key Vault — the audit trail rarely flatters anyone. The articles cover integration patterns with Azure Key Vault, hardware-backed signing, and rotation schedules that match the threat model rather than the calendar.

A separate cluster of content addresses ISO/IEC 27001 Annex A.8.24 and the engineering decisions it implies. Compliance is rarely about which algorithm is selected; it is about whether key custody, rotation evidence, and incident response procedures hold up under scrutiny. The articles document concrete patterns for personally identifiable information, authentication tokens, and any data requiring confidentiality in cloud-native .NET applications deployed to Azure.

The recurring message: stop rolling your own crypto. The libraries exist, the patterns are documented, and the audit will not be sympathetic to clever shortcuts.

Your Encryption Is Broken — .NET Data Protection Done Right

Your Encryption Is Broken — .NET Data Protection Done Right

Every developer who has tried simple encryption with XOR and hardcoded keys eventually faces the audit that exposes their house of cards. I’ve watched production systems fail compliance assessments because someone believed base64 encoding was good enough or that compilation obscures secrets. The .NET Data Protection API exists precisely because Microsoft’s cryptography team spent years solving problems most developers don’t know they have. This isn’t about learning yet another library—it’s about understanding why professional implementations outperform clever hacks, and how Azure Key Vault integration transforms theoretical security into auditable compliance.