5.2 Basic factors

5.2.1 Network Model

Among the 3 available network models (synchronous, asynchronous and semi-synchronous), we chose the synchronous model, which is a synchronous protocol, according to the SCP requirements.

It is a well-known result in the field of consensus research that no protocol can have activity (ensuring that the network progresses), security (ensuring that all participants reach the same result), and fault tolerance (ensuring that the network can safely progress if one or more nodes do not respond). This result, called FLP Impossibility, is frequently cited in SCP documents for its emphasis on security over activeness. On the other hand, fault tolerance is a requirement for any system with open membership.

Random Source

Parts of this paper rely on pseudo-random data, such as signature schemes. The accuracy cannot be verified due to the unpredictable nature of random

Ensuring the randomness of a distributed system relies on the seed data provided by all participants. This makes it a challenge to ensure that no participant is better at producing or deferring their seed data than any other participant.

Using the hash and its original image as seed data can do this.

At registration, the verifier chooses a random value and performs n hash operations, and submits the final value as its initial seed data. Whenever new seed data is needed, the verifier can find the original image of its last published seed data, thus ensuring true randomness without the ability to manipulate the data.

However, a problem arises when the verifier is willing to keep the network data. If releasing data leads to worse results compared to retaining it, then a node may choose to selectively retain its original image, suspend the network or deviate from the results. To avoid falling into this trap, verifiers should regularly release (and listening verifiers should support) enough seed data to survive small disruptions. If reasonable intervals are introduced in the consensus protocol, it can be ensured that early release of the original image by the verifier does not lead to weakened security guarantees, allowing it to cope with temporary outages.

Transaction anonymity protection

King Tribe ensures the anonymity of transaction information in terms of both transaction unlinkability and untraceability, and is constantly iterating to improve anonymity protection. King Tribe defines transaction unlinkability, where no two external transactions can be proven to have been sent to the same person, and untraceablility, where all possible senders are probabilistically equal for each internal transaction.

Unconnectedness and untraceability are properties that must be met by a strong privacy-preserving blockchain. King Tribe supports unlinkability and untraceability by using one-time secret key and ring signature technology. At the same time, King Tribe designs and implements a strict zero-knowledge proof model as an optional feature to further enhance transaction anonymity.

One time key

King Tribe uses one-time key technology to make transactions uncorrelated. One-time key means that the sender uses a separate key for each transaction to sign. Unlike the usual blockchain transactions where the receiver uses only one pair of public and private keys, in the one-time key scheme, the receiver needs to use two pairs of public and private keys in each transaction.When a transaction is initiated, the transaction sender uses the two public keys of the transaction recipient and a random number to generate a temporary public key, the sender uses the temporary key as an address for the transaction, and the recipient performs a Diue-Hellman exchange and combines it with one of his private key messages to obtain the temporary private key. Since only the receiver can verify the key at one time, the correctness of the transaction is guaranteed. Also, each transaction uses a different random number, and even if multiple transactions are made with the same receiver, they cannot be correlated because their primary keys are different, ensuring that the transactions are uncorrelated.

Ring Signature

One time key mainly guarantees the privacy of the receiver of the transaction, in order to also guarantee the privacy of the sender of the transaction. In-terValue uses ring signature technology. The ring signature is a multi-user signature technique derived from the Group Signature technology, which eliminates many disadvantages of the group signature, such as eliminating the need for a group administrator and being untraceable. The ring signature model is shown in the figure below.

In ring signature technology, the message is signed by a group of signers and the verifier cannot know who is the specific signer. Therefore, ring signature is a good solution to the problem of protecting the identity of the signer and achieving untraceability of the transaction. On the other hand, because the general ring signature technique hides the signer among a group of users, it brings the problem of double spending, which can be solved by using linkable ring signature technique.