[AES-256 VS CHACHA20]

Two excellent ciphers, one practical difference: whether your processor has AES built in.

CryptFile.Online lets you encrypt files with either AES-256-GCM or ChaCha20-Poly1305. Both are modern, both are used to protect most of the web's traffic in TLS 1.3, and neither has a known practical attack. Choosing between them is about speed and robustness on different devices, not about security level.

[SIDE BY SIDE]

  • Key size: 256 bits for both.
  • Authentication: both are AEAD constructions — AES with GCM, ChaCha20 with Poly1305 — so any modification of the ciphertext is detected on decryption.
  • Design: AES (2001) is a block cipher selected by NIST; ChaCha20 (2008, by Daniel J. Bernstein) is a stream cipher built only from additions, rotations and XORs.
  • Speed with hardware support: AES wins. Almost every desktop and laptop processor since about 2010, and most phones since about 2015, have AES instructions built in.
  • Speed without it: ChaCha20 wins clearly — which is why Google adopted it for older Android phones.
  • Where you meet them: AES in disk encryption (BitLocker, FileVault), Wi-Fi and most TLS connections; ChaCha20 in WireGuard VPNs, as OpenSSH's default cipher, and in TLS on devices without AES hardware.

[WHY CHACHA20 IS CONSIDERED ROBUST]

Software implementations of AES that do not use the dedicated instructions rely on lookup tables, and the time those lookups take can leak information about the key to an attacker sharing the machine (a "cache-timing" attack). ChaCha20's simple operations run in constant time naturally, so even a straightforward implementation is safe.

In a browser, both are provided by well-reviewed libraries, so this matters more to protocol designers than to you.

[WHICH TO CHOOSE]

  • Not sure? Use AES-256-GCM. It is the default, it is fastest on nearly every current device, and it is the most widely recognised standard — useful if you must follow a policy that names an algorithm.
  • Use ChaCha20-Poly1305 on an older or low-end phone, or if you simply prefer a cipher designed for constant-time software implementations.

The choice is stored in the encrypted file's header, so whoever decrypts it does not need to know which one you picked.

[WHAT MATTERS MORE THAN THE ALGORITHM]

Both ciphers are far stronger than the password that protects the key. A short or reused password is the realistic weak point: CryptFile.Online slows guessing down with 600,000 rounds of PBKDF2 — the level OWASP recommends — but a six-letter password is still guessable.

Use four or more random words, or let the tool generate a random key. That decision does more for your security than the choice of cipher.

[FREQUENTLY ASKED QUESTIONS]

Is AES-256 or ChaCha20 more secure?

Neither, in practice. Both use 256-bit keys and have no known practical attacks. The difference is performance on different hardware and how easy each is to implement safely.

Can quantum computers break them?

Grover's algorithm would roughly halve the effective strength of a symmetric key, leaving 256-bit AES and ChaCha20 with about 128 bits of security — still considered secure. The algorithms threatened by quantum computers are public-key ones such as RSA.

Do I need to remember which algorithm I used?

No. The algorithm is recorded in the .enc file header and detected automatically when you decrypt.