Guarantee of ledger immutability

A method, comprising:

• connecting, by an attester node, to a blockchain network A configured to store hashes of blocks A;
• coupling, by the attester node, the blockchain network A with a blockchain network B configured to store hashes of blocks B;
• receiving, by the attester node, a request from the blockchain network A to send a hash of a block A produced at a time t1 (AHash_1) to the blockchain network B;
• confirming, by the attester node, that the blockchain network A has stored a hash of a block B produced at a time t0 (BHash_0);
• sending, by the attester node, the AHash_1 to the blockchain network B to be stored;
• receiving, by the attester node, a hash of the block B produced at the time t1 (BHash_1) from the blockchain network B;
• confirming, by the attester node, that the blockchain network B has stored a hash of a block A produced at the time t0 (AHash_0);
• and
• providing, by the attester node, the BHash_1 to the blockchain network A to be stored,
• wherein the t0 is less than the t1.

A non-transitory computer readable medium comprising instructions, that when read by a processor, cause the processor to perform:

• connecting to a blockchain network A configured to store hashes of blocks A;
• coupling the blockchain network A with a blockchain network B configured to store hashes of blocks B;
• receiving a request from the blockchain network A to send a hash of a block A produced at a time t1 (AHash_1) to the blockchain network B;
• confirming that the blockchain network A has stored a hash of a block B produced at a time t0 (BHash_0);
• sending the AHash_1 to the blockchain network B to be stored;
• receiving a hash of the block B produced at the time t1 (BHash_1) from the blockchain network B;
• confirming that the blockchain network B has stored a hash of a block A produced at the time t0 (AHash_0);
• and
• providing the BHash_1 to the blockchain network A to be stored, wherein the t0 is less than the t1.