What is DES?
DES decryption reverses DES encryption, turning ciphertext back into plaintext using the same 56-bit key, mode, IV and padding that were used to encrypt. DES is a symmetric cipher, so the same secret key is required. DES is no longer secure, so use this mainly for legacy data; for new systems use AES. Decryption runs entirely in your browser.
Match the settings: decryption needs the same key, mode, IV and padding used to encrypt. Runs locally in your browser.
How DES works
DES decryption runs the cipher with the round subkeys reversed:
- The same 56-bit key produces the 16 round subkeys.
- Each block runs the 16 Feistel rounds in reverse order.
- The mode and IV undo the chaining between blocks.
- Padding is removed to recover the exact original data.
How to use
- Paste the DES ciphertext.
- Enter the same key and settings used to encrypt.
- The decrypted text appears in the output.
Options explained
- Mode — Must match the mode used to encrypt (ECB, CBC, CFB, OFB).
- IV — Provide the same IV used during encryption.
- Padding — Must match (PKCS5/PKCS7 or NoPadding).
Common uses
- Reading DES-encrypted legacy data.
- Migrating old encrypted records.
- Interoperability testing.
Frequently asked questions
Why does decryption fail?
The key, mode, IV or padding does not match what was used to encrypt.
Is DES still safe?
No — use it only for legacy data; choose AES for new work.
How do I encrypt instead?
Use the DES Encryption tool.