AES-256 File Encryption

Training & Educational Use Only — This tool demonstrates AES-256-GCM encryption concepts for educational purposes. Do not use it to protect classified information, CUI, or any data subject to CMMC, DFARS, ITAR, or HIPAA controls. For regulated data, use approved and certified encryption solutions.

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Drop any file here to encrypt

Click to browse · Any file type · Processed locally

Generated AES-256 Key

⚠ Save this key before downloading This key is generated fresh for every file and is never stored anywhere. If you lose it, the encrypted file cannot be recovered — ever. Copy it and store it somewhere safe before you download the encrypted file.

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Drop your .enc file here to decrypt

Click to browse · Must be a .enc file from this tool

Paste your AES-256 key

Step 01

Key Generation

The browser's Web Crypto API generates a cryptographically random 256-bit key. This is not a passphrase — it's true randomness from your operating system's entropy source.

Step 02

Encryption

A random 96-bit Initialization Vector (IV) is generated. Your file is encrypted with AES-256-GCM using the key and IV. The IV is prepended to the encrypted output so decryption is possible.

Step 03

Authentication Tag

GCM mode produces a 128-bit authentication tag. When decrypting, this tag verifies the file hasn't been tampered with. If even one byte was changed, decryption fails.

Algorithm	AES-256-GCM (Advanced Encryption Standard, Galois/Counter Mode)
Key length	256 bits — the same key length used for Top Secret US government data
IV length	96 bits, randomly generated per file
Auth tag	128 bits — provides integrity verification in addition to confidentiality
Key format	Hexadecimal string (64 characters = 32 bytes = 256 bits)
Output format	IV (12 bytes) + Ciphertext + Auth Tag — saved as .enc file
Crypto engine	Browser Web Crypto API (SubtleCrypto) — FIPS 140-2 compliant in most implementations
Data handling	File never leaves your browser. No network requests made during encryption or decryption.

Why GCM mode matters: AES can be used in several modes. GCM (Galois/Counter Mode) provides both confidentiality and authenticity — it encrypts your data AND produces a tag that proves it hasn't been altered. Older modes like CBC only provide confidentiality. NIST recommends GCM for most applications, and it's the mode used in TLS 1.3, the protocol securing most HTTPS traffic today.

Key management is everything: AES-256 has never been broken. Every real-world failure of AES-encrypted data is a key management failure — the key was stored insecurely, transmitted in plaintext, or lost. This tool generates strong keys. What you do with that key is the security-critical decision.