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Security and Cryptography Basics for Developers

Last updated: 27 September 2026

Encoding, hashing, and encryption solve different problems. Base64 changes how bytes are written and is easy to reverse. A hash produces a fixed-size digest. Encryption protects content only when the key and the way you use it are appropriate.

Ask what you are protecting against

For checking whether a downloaded file matches a published checksum, compare hashes from a trusted source. For password storage, use a password hashing algorithm designed to be slow, not a plain fast hash. For confidentiality, choose authenticated encryption and protect the key; hiding the ciphertext is not the same as protecting the secret.

Treat generated secrets as secrets

A key or token is useful only if it is generated securely and kept out of logs, URLs, screenshots, and shared documents. A tool may process data locally and still leave it in clipboard history or a downloaded file. Check what your workflow exposes.

  • AES Encryption — Encrypt and decrypt text with AES.
  • Base64 Text — Encode and decode UTF-8 text to and from Base64, URL-safe optional.
  • bcrypt — Hash a password with bcrypt, or verify one against a hash.
  • BIP39 Mnemonic — Generate a BIP39 mnemonic phrase and derive its seed.
  • File Hash Checker — Hash a file with MD5, SHA-1, SHA-256 and SHA-512, and check it against a published digest.
  • Hash Text — Compute MD5, SHA-1, SHA-256 and SHA-512 digests of text.
  • HMAC Generator — Compute keyed HMAC signatures with a choice of digest.
  • OTP Generator — Generate and verify time-based one-time passwords.
  • Password Strength — Estimate how long a password would take to crack.
  • Random Generator — Pick from a list with a spin wheel, slot machine, random card, dice or ticker animation.
  • RSA Key Pair — Generate an RSA public and private key pair, and check whether two keys match.
  • SNAP BI Asymmetric Signature — Build, sign and verify the SHA256withRSA signature used by Bank Indonesia’s SNAP BI standard.
  • SSH Key Generator — Generate an Ed25519, ECDSA or RSA key pair, with the OpenSSH public key and fingerprints.
  • Token Generator — Generate random tokens and passwords of a chosen length and charset.