What is DES?
DES (Data Encryption Standard) is a symmetric block cipher standardized by NIST in 1977. It encrypts data in 64-bit blocks using a 56-bit key and the same key both encrypts and decrypts. DES was the world standard for decades, but its short 56-bit key can now be brute-forced quickly with modern hardware, so it is considered insecure. Use DES only for interoperability with legacy systems; for new work choose AES. This tool runs DES entirely in your browser.
Legacy only: DES is insecure for modern use (its 56-bit key is brute-forceable). Use AES for new systems. Encryption runs locally in your browser.
How DES works
DES is a Feistel cipher that scrambles each 64-bit block:
- The 56-bit key is expanded into 16 round subkeys.
- Each 64-bit block is split in half and passed through 16 rounds of substitution (S-boxes) and permutation.
- A cipher mode (CBC, ECB, …) and an IV chain the blocks together.
- Padding fills the final block to the 8-byte boundary.
How to use
- Enter the text you want to encrypt.
- Provide a key (and IV/mode settings where required).
- The encrypted output is produced in your browser.
- Share the ciphertext; share the key only through a safe channel.
Options explained
- Mode — ECB, CBC, CFB or OFB. Avoid ECB; prefer CBC with a random IV.
- IV — An initialization vector used by modes like CBC so identical blocks differ.
- Padding — PKCS5/PKCS7 pads the last block; NoPadding requires block-aligned input.
- Key / passphrase — Provide a raw key or derive one from a passphrase with a salt and iterations.
Common uses
- Interoperating with old systems that still use DES.
- Maintaining or migrating legacy data.
- Learning how classic block ciphers work.
Frequently asked questions
Is DES secure?
No. Its 56-bit key is too short and can be brute-forced. Use AES instead.
What is the DES key size?
56 effective bits (supplied as 64 bits including parity).
How do I decrypt DES?
Use the DES Decryption tool with the same key, mode, IV and padding.