Your Encrypted Backups Are Slow Because Encryption Isn't the Bottleneck

If you encrypt files before pushing them to backup storage, you've probably assumed the encryption step is what makes it slow. That's what I assumed too. Then I looked at the numbers. On any modern x86 chip with AES-NI, AES-256-GCM runs at 4-8 GB/s on a single core. ChaCha20-Poly1305 isn't far behind. The CPU is not the problem. The problem is that your encryption tool reads a chunk of data, encrypts it, writes it out, then reads the next chunk. It's serial. The disk sits idle while the CPU works, and the CPU sits idle while the disk works. One person decided to fix that by applying the same async I/O technique that powers modern databases to file encryption. The result hits GB/s throughput on commodity NVMe hardware, and the whole thing is about 900 lines of Rust. What Is Concryptor? Concryptor is a multi-threaded AEAD file encryption CLI built by FrogSnot. It encrypts and decrypts files using AES-256-GCM or ChaCha20-Poly1305 with Argon2id key derivation, and it does it fast by overla