Choosing Secure Encryption Algorithms: A Practical Guide

“Encrypt the data” sounds like one decision, but the right method depends on what you need to protect and where the keys live. Encrypting a database backup, verifying a downloaded file and storing a user password are different jobs. Using one primitive for all three usually creates avoidable risk.

Match the primitive to the task

• Encryption protects confidentiality and can be reversed by someone holding the key.
• A cryptographic hash produces a fixed-size digest for integrity checks; it is not a way to recover the original data.
• Password hashing deliberately makes guessing expensive and uses a salt. Applications should use a password-hashing API such as Argon2id or bcrypt, not plain SHA-256.

For application data, use a maintained cryptographic library and an authenticated-encryption mode such as AES-GCM or ChaCha20-Poly1305 when supported. Authentication matters: it lets the receiver detect tampering as well as decrypting the message. The NIST GCM specification describes one standardized authenticated-encryption mode.

Keys are part of the design

Do not hard-code encryption keys beside the ciphertext or commit them to a repository. Restrict which service identities can use a key, define how it is backed up and rotated, and decide how old data will be re-encrypted if a key is replaced. Losing a key can make a good backup unusable; exposing it can make strong encryption irrelevant.

Do not invent a cryptographic protocol

Avoid choosing an algorithm because a short blog post calls it “unbreakable.” Avoid obsolete algorithms and unauthenticated modes for new designs. Defaults and library support change, so check the version and official guidance for the stack you deploy.

For file checksums, use a hash such as SHA-256 to compare a file with a trusted reference. That detects a mismatch only when the expected digest itself comes from a trustworthy channel. A digest published beside a malicious download is not independent proof of authenticity.