Interactive Online Simulation of the A5/1 Cipher

A5/1 is a cipher developed in 1987 to protect the voice communication in mobile networks according to the GSM standard. It is now regarded as broken.

This is a simplified simulation of the cipher (without the "frame counter" step before register initialization). It consists of three steps:

  1. The key must first be read in completely (64 single steps since 64 bits)
  2. Then the register is initialized (100 single steps)
  3. An arbitrarily long key stream can now be generated
The key stream is linked to the plaintext (XOR) at the sender and thus the secret text is formed, which can then be transmitted. The same key stream is formed at the receiver, which is then linked to the secret text, in order to receive the clear text again.

Tip: If you don't want to click many times, then you can click on the desired button and then continue with the Enter key instead of clicking mouse left key.

The Key (64 bit)

0/100

maj(x8, y10, z10) = maj(0, 0, 0) = 0

Keystream (0 bits generated)

Register 1

x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 x10 x11 x12 x13 x14 x15 x16 x17 x18

Register 2

y0 y1 y2 y3 y4 y5 y6 y7 y8 y9 y10 y11 y12 y13 y14 y15 y16 y17 y18 y19 y20 y21

Register 3

z0 z1 z2 z3 z4 z5 z6 z7 z8 z9 z10 z11 z12 z13 z14 z15 z16 z17 z18 z19 z20 z21 z22

Explanation: Blue register names, indicate that this register stepped.

Implemented by Bastian Raschke and Nils Tegetmeyer and Amir Khazaie.