Is AES-128 strong enough?

Yes. AES-128 offers 128 bits of security with no practical attacks, which is sufficient for virtually all uses today. AES-256 adds margin against future cryptanalysis and quantum Grover-style attacks but is not strictly required for most data.

Why is ECB mode considered insecure?

ECB encrypts each block independently, so identical plaintext blocks produce identical ciphertext blocks. This leaks structure — the classic ECB penguin image stays visible. Never use ECB for real data; use an AEAD mode like GCM instead.

When should I pick ChaCha20 over AES?

ChaCha20-Poly1305 is a great choice on devices without AES hardware acceleration, where it runs faster and more constant-time than software AES. On modern CPUs with AES-NI, AES-GCM is typically faster.

AEAD stands for Authenticated Encryption with Associated Data. It provides confidentiality and integrity in one operation, so the recipient detects tampering. AES-GCM and ChaCha20-Poly1305 are the standard AEAD schemes.

What is the Symmetric Cipher Reference?

Reference for symmetric encryption algorithms including AES, ChaCha20, 3DES and Blowfish with key length, block size, secure modes, AEAD support and deprecation notes. It runs free in your browser on Gera Tools, with nothing uploaded.

Symmetric Cipher Reference

Name: Symmetric Cipher Reference
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Symmetric cipher reference

Symmetric ciphers use the same secret key to encrypt and decrypt. They are fast and used for bulk data: TLS records, disk encryption, file encryption and tokens. This reference compares AES, ChaCha20, 3DES, Blowfish and others by key size, block size, the recommended mode of operation, and current security status.

Block ciphers vs stream ciphers

A block cipher (AES, 3DES) encrypts a fixed-size block of bits at a time — typically 128 bits for AES or 64 bits for 3DES. To encrypt a message longer than one block, a mode of operation chains the blocks together.

A stream cipher (ChaCha20) generates a continuous pseudorandom keystream and XORs it byte-by-byte with the plaintext, working naturally on arbitrary-length data without block-padding logic.

Modes of operation

The cipher algorithm itself is rarely the vulnerability — the mode usually is:

Mode	Authentication	Notes
GCM (AEAD)	Built-in	Preferred for most uses. Fast with AES-NI. Nonce reuse is catastrophic.
ChaCha20-Poly1305 (AEAD)	Built-in	Preferred on hardware without AES acceleration.
CCM (AEAD)	Built-in	Used in constrained environments (802.11, Bluetooth).
CBC	External MAC needed	Vulnerable to padding-oracle attacks without careful implementation.
CTR	External MAC needed	Parallelisable, but nonce management is the developer’s responsibility.
ECB	None	Never use. Identical plaintext blocks produce identical ciphertext blocks.

Choosing the right cipher

New systems: Default to AES-256-GCM. It is hardware-accelerated on every modern processor via AES-NI and offers 256-bit keys with authenticated encryption in one operation.

No AES hardware acceleration: Choose ChaCha20-Poly1305. It is constant-time in software, resistant to timing side-channels, and used widely in TLS 1.3, SSH, and WireGuard.

Migrating legacy code: If you are still on 3DES or RC4, migrate. 3DES has a 64-bit block size that makes it vulnerable to Sweet32 birthday attacks on long sessions, and it is deprecated by NIST. RC4 is fully broken.

The nonce problem

Both AES-GCM and ChaCha20-Poly1305 require a unique nonce (number used once) per encryption under the same key. Reusing a GCM nonce with the same key is catastrophic: it leaks the authentication key and makes all messages under that key-nonce pair decryptable. In practice, generate a random 96-bit nonce per message (the collision probability at scale is negligible) or use a deterministic counter that never repeats.

Key size context

AES-128 provides 128 bits of security — no practical attack exists today, and it is sufficient for virtually all applications. AES-256 provides extra margin against future cryptanalysis and partially mitigates Grover’s algorithm for hypothetical quantum attackers (reducing effective security to 128 bits under Grover). In practice the choice of mode and nonce discipline matters far more than the key length jump from 128 to 256 bits.

Quick decision guide

Store a file or a database column → AES-256-GCM with a random nonce stored alongside the ciphertext.
TLS record or network packet → handled by the TLS 1.3 handshake (usually AES-GCM or ChaCha20-Poly1305 negotiated automatically).
Embedded / IoT / no AES-NI → ChaCha20-Poly1305.
Legacy interop requiring 3DES → plan a migration; never build new code around it.