🔍 Crypto Is Easy to Use—and Easier to Misuse

Modern cryptographic libraries have made it easy to add encryption, signing, and hashing to applications. But easy APIs can hide dangerous defaults, and even small implementation mistakes can undermine everything cryptography is meant to protect.

This post explores the most common—and most costly—cryptographic misuse patterns seen in audits, open source, and production environments. Whether you’re a developer, architect, or security reviewer, these patterns are worth watching for.

🔓 Hardcoded Secrets

• Issue: Developers store private keys, passwords, or encryption keys directly in source code.
• Impact: Anyone with source access or repo leaks gains full decryption capability.
• Seen in: IoT firmware, mobile apps, GitHub repos, container images

🔑 Fix: Use secure secret managers (e.g., AWS Secrets Manager, HashiCorp Vault). Never commit secrets to version control.

⚠️ Weak or Deprecated Algorithms

• Issue: Using broken or outdated algorithms like MD5, SHA1, DES, or RC4.
• Impact: Allows attackers to forge signatures, break hashes, or decrypt with trivial effort.

🔑 Fix: Use modern, vetted algorithms: AES-GCM for encryption, SHA-256 or higher for hashing, and avoid anything with known collisions.

📏 ECB Mode Encryption

• Issue: Using AES in ECB (Electronic Codebook) mode, which encrypts blocks independently.
• Impact: Leaks patterns in the plaintext, making the ciphertext vulnerable to analysis.

🔑 Fix: Always use block cipher modes with randomization and integrity protection (e.g., AES-GCM, AES-CBC with HMAC).

🪪 Insecure Token Construction

• Issue: Homegrown session tokens or API keys using predictable strings or timestamps.
• Impact: Predictable or forgeable tokens enable privilege escalation and impersonation.

🔑 Fix: Use well-established libraries like JWT (with signed claims), UUIDv4 for randomness, or OAuth standards for identity assertions.

🚫 Skipping Certificate Validation

• Issue: Disabling or skipping certificate validation in TLS clients (e.g., verify=False in Python requests).
• Impact: Leaves users vulnerable to man-in-the-middle attacks and spoofed servers.

🔑 Fix: Always validate server certificates. Pin public keys or use custom root CAs if needed—but never skip validation.

🧪 Predictable or Reused IVs

• Issue: Using static or reused initialization vectors (IVs) in symmetric encryption.
• Impact: Breaks semantic security and may leak relationships between encrypted data.

🔑 Fix: Use a new, cryptographically random IV for each encryption operation. Many libraries do this for you—use them properly.

🔁 Homegrown Cryptography

• Issue: Rolling your own crypto logic (e.g., making a custom hash, padding scheme, or signature format).
• Impact: Nearly always introduces vulnerabilities that real attackers can exploit.

🔑 Fix: Use mature, audited libraries with conservative defaults. If you’re writing your own crypto, you’re probably doing it wrong.

🔍 What to Look for in Code Reviews

When reviewing code for cryptographic misuse, look for:

• Hardcoded strings labeled key, token, or secret
• Use of insecure hash functions (e.g., md5(), sha1())
• Encryption calls with ECB mode or missing IVs
• Skipped or suppressed TLS certificate validation
• Custom crypto logic or reinvented protocols

If it looks clever, it might be dangerous.

📣 Final Thought

The best cryptographic algorithms in the world are useless if applied incorrectly. From hardcoded secrets to broken ciphers, crypto misuse remains one of the most common and preventable vulnerabilities in modern applications.

Need help performing secure code reviews, integrating cryptographic standards, or eliminating crypto misconfigurations? Let’s talk.