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Ring Signatures And Anonymisation – Coinmonks – Medium

Ring Signatures And Anonymisation

A demo of the methods involved in this article is here.

And so there has been a leak of information at the White House. Donald Trump calls in his Cyber Security leads, and tells them, “I know one of you leaked the information, but I can’t tell which one”. How can Donald tell that one of his leads has leaked the information, but not know which one? Well this can be achieved with a ring signature, and which provides anonymity, unforgivably and collusion resistance.

A ring signature is a digital signature that is created by a member of a group which each have their own keys. It is then not be possible to determine the person in the group who has created the signature. The method was initially created by Ron Rivest, Adi Shamir, and Yael Tauman in 2001, and in their paper they proposed the White house leak dilemma.

Creating the ring

In a ring signature we define a group of entities who each have their own public/private key pairs of (P1, S1), (P2, S2), …, (Pn, Sn). If we want an entity i to sign a message (message), they use their own secret key (si), but the public keys of the others in the group (m,si,P1…Pn). It should then be possible to check the validity of the group by knowing the public key of the group, but not possible to determine a valid signature if there is no knowledge of the private keys within the group.

So let’s say that Trent, Bob, Eve and Alice are in a group, and they each have their own public and secret keys. Bob now wants to sign a message from the group. He initially generates a random value v, and then generates random values (xi) for each of the other participants, but takes his own secret key (si) and uses it to determine a different secret key, and which reverse of the encryption function. He now takes the message and takes a hash of it, and thus creates a key (k). This key will be used with symmetric encryption to encrypt each of the elements of the ring (Ek), and then each...

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