What Is AES-256-GCM?
AES-256-GCM stands for Advanced Encryption Standard, 256-bit key, Galois/Counter Mode. It combines three powerful cryptographic concepts working together.
AES (Advanced Encryption Standard)
AES was established as the US Federal standard in 2001 by NIST. It is a symmetric block cipher — the same key both encrypts and decrypts data. The data is processed in 128-bit blocks through multiple transformation rounds.
256-bit Key Size
The "256" refers to the key length in bits. A 256-bit key means 2²⁵⁶ possible key combinations — approximately 10⁷⁷. There are roughly 10⁷⁸ to 10⁸² atoms in the observable universe. Even with all computing power on Earth, cracking a 256-bit key would take longer than the age of the universe.
GCM (Galois/Counter Mode)
GCM is the mode of operation — how AES processes data in practice. It provides two critical properties:
1. Confidentiality — data is encrypted and cannot be read 2. Authenticity — a 128-bit authentication tag detects any tampering
This is called authenticated encryption. Without authentication, an attacker who intercepts encrypted data could flip bits and modify it without detection. GCM's auth tag makes any modification immediately apparent.
How VaultSends Implements AES-256-GCM
VaultSends layers multiple protections:
Algorithm: AES-256-GCM (authenticated encryption)
Key Size: 256 bits
Auth Tag: 128 bits (prevents tampering)
IV Size: 128 bits (random per secret)
Salt: 256 bits (random per secret)
KDF: PBKDF2-SHA512
KDF Iterations: 310,000 (NIST 2023 recommended minimum)Key Derivation with PBKDF2-SHA512
Rather than using a passphrase directly as an AES key, VaultSends runs it through PBKDF2-SHA512 at 310,000 iterations. Each password guess takes approximately 0.3 seconds on modern hardware. Combined with rate limiting and IP blocking, brute force is practically impossible for any strong passphrase.
Unique Salt and IV Per Secret
Every secret gets a unique 256-bit random salt and 128-bit random IV. This means even if two people encrypt the same password, the ciphertexts are completely different and cannot be correlated.
Why Zero-Knowledge Matters
VaultSends combines AES-256-GCM with a zero-knowledge architecture. We store only encrypted ciphertext — never your plaintext. Your passphrase is never transmitted or stored. Even our own servers cannot decrypt your data. A database breach exposes only unusable encrypted bytes.
This is the same architecture used by major password managers and secure messaging apps.