Cryptography Essentials for Developers

Cryptography helps protect data both at rest and in transit. As a developer, you don’t need to become a cryptography expert, but knowing a few basics helps you ship safer software.

In simple terms, encryption turns plaintext into ciphertext using a key. Two common setups exist: symmetric encryption, which uses the same key to lock and unlock data, and asymmetric encryption, which uses a public key to encrypt and a private key to decrypt. Hashing creates a fixed, short fingerprint of data and is useful for integrity and password storage when used correctly.

Understanding keys and encryption

Symmetric encryption is fast and efficient for large data. It is ideal for databases and files, with AES in authenticated modes like AES-GCM being a popular choice. Asymmetric encryption is slower but lets you share keys safely; it enables key exchange and digital signatures. Examples include RSA and elliptic curve schemes such as P-256.

  • Symmetric: fast, good for bulk data; requires secure key storage
  • Asymmetric: uses a key pair; supports key exchange and identity

Hashing creates a fingerprint of data, but it is not encryption. It is one-way and cannot be reversed. For secrets like passwords, use specialized password-hash schemes.

  • Hashing is one-way and not reversible
  • Use bcrypt, scrypt, or Argon2 for passwords

Practical guidance for developers

Rely on trusted libraries rather than writing crypto code yourself. In browsers, use WebCrypto; on servers, rely on libsodium, OpenSSL, or your platform’s crypto services.

  • Use authenticated encryption: AES-GCM or ChaCha20-Poly1305
  • Enable TLS for all network traffic and keep libraries up to date
  • Do not roll your own crypto or create new algorithms

Key management basics

Keys are core assets. Do not hard-code them in source or store them in plaintext. Use a dedicated key store or cloud KMS with strict access control. Rotate keys regularly and keep audit logs.

  • Use a vault or KMS
  • Separate duties and audit access
  • Rotate keys and retire old material

Putting it into practice

Think in layers: encrypt data at rest, protect data in transit, and sign important messages when needed.

  • Encrypt sensitive fields in databases and backups
  • Use TLS everywhere; prefer modern ciphers and HSTS
  • Consider digital signatures for important communications

Remember, you don’t have to become a crypto expert, but a practical mindset helps you avoid common mistakes and build safer apps.

Key Takeaways

  • Use established crypto libraries and avoid custom implementations.
  • Encrypt data at rest and in transit with authenticated schemes.
  • Protect and rotate keys with a dedicated system and proper access controls.