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SPECK Encryption & Decryption

Encrypt and decrypt with SPECK 64/128, the NSA lightweight block cipher that ISO declined to standardise.

Input

Output (Base64)

SPECK is broken or obsolete. It is here to read data that already exists — never use it to protect anything new. Use AES-GCM instead.
Everything is processed locally in your browser. Your data never leaves this device.

Small ciphers for small devices

XXTEA and SPECK exist because AES is large: a full implementation needs S-box tables and a key schedule that a microcontroller with a few kilobytes of memory cannot spare. Both fit in a handful of lines.

XXTEA is the third revision of TEA and operates on a whole message rather than fixed blocks, embedding the length in its output — which is why a wrong key is usually detected rather than producing plausible garbage.

SPECK was published by the NSA. No break is known, but ISO declined to standardise it after members raised trust concerns, and that is the reason it is uncommon outside firmware.

Frequently asked questions

Are these safe to use?

Neither has a published break, but neither has AES's two decades of scrutiny either. On anything that can run AES — which is any browser, phone or server — use AES-GCM.

Why does XXTEA reject my key?

It does not reject keys; it rejects output whose embedded length does not match, which is what a wrong key produces. Check the key and that the ciphertext was produced by XXTEA.

What key length does SPECK need?

This page implements SPECK 64/128, so the key is 16 bytes. Shorter input is zero-extended, which weakens it — supply a full 16 bytes.

Related tools

XXTEA Encryption & DecryptionEncrypt and decrypt with XXTEA (Corrected Block TEA) — tiny enough to fit in a few lines, and common in game and embedded code.AES Encryption & DecryptionEncrypt and decrypt text with AES-GCM or AES-CBC using a passphrase. The salt and IV travel with the ciphertext, so nothing else has to be kept.RSA Key Pair GeneratorGenerate an RSA key pair in your browser and export it as PKCS#8 / SPKI PEM or JWK. The private key never leaves the page.RSA Sign & VerifySign a message with an RSA private key and verify it with the public key, using RSASSA-PKCS1-v1_5 or RSA-PSS.RSA Encryption & DecryptionEncrypt a short message with an RSA public key (RSA-OAEP) and decrypt it with the private key.ECDSA Key Pair GeneratorGenerate an elliptic-curve key pair (P-256, P-384 or P-521) as PEM or JWK — far smaller than RSA at the same security level.