Epoch-based cross-chain verification

1 . A computer-implemented method for verifying messages in a blockchain system, the method comprising:

receiving a proposed block on a first blockchain, the proposed block including (i) a latest secondary-chain block height and (ii) an epoched secondary-chain block height associated with a second blockchain;

determining whether the proposed block seals a current epoch by comparing a timestamp of the proposed block with an epoch duration threshold;

in response to determining that the proposed block is a sealing block of the current epoch:

(i) assigning a next block an updated epoched secondary-chain block height equal to the latest secondary-chain block height included in the sealing block, and

(ii) advancing to a next epoch; and

verifying one or more messages included in the next block using a validator set obtained from the second blockchain at the epoched secondary-chain block height assigned to the next block, wherein all blocks within an epoch are verified against a same validator set.

2 . The computer-implemented method of claim 1 , further comprising identifying the latest secondary-chain block height, the epoched secondary-chain block height, an epoch number, a minimum epoch duration, and an epoch start time from a block header of the proposed block.

3 . The computer-implemented method of claim 1 , wherein the epoch duration threshold is computed as an epoch start time plus a minimum epoch duration parameter defined by a virtual machine associated with the first blockchain.

4 . The computer-implemented method of claim 1 , further comprising monotonically increasing, for each newly proposed block, a latest secondary-chain block height pointer corresponding to a most recent secondary-chain block height observable by the first blockchain at a timestamp of the newly proposed block.

5 . The computer-implemented method of claim 1 , wherein the sealing block is included in the current epoch and the next block is included in the next epoch.

6 . The computer-implemented method of claim 1 , further comprising obtaining, at a block height corresponding to the epoched secondary-chain block height, a validator set recorded on the second blockchain.

7 . The computer-implemented method of claim 1 , wherein the latest secondary-chain block height is set by a block builder.

8 . The computer-implemented method of claim 1 , further comprising, in response to determining that the proposed block does not seal the current epoch, assigning to the next block the epoched secondary-chain block height included in the proposed block.

9 . The computer-implemented method of claim 1 , wherein advancing to the next epoch further comprises:

incrementing an epoch number; and

assigning the incremented epoch number to the next block.

10 . The computer-implemented method of claim 1 , further comprising:

performing a single lookup of a next validator set from the second blockchain at the updated epoched secondary-chain block height assigned to the next epoch;

storing the next validator set for a duration of the next epoch; and

verifying blocks proposed for the duration of the next epoch using the stored next validator set.

11 . A system for verifying messages in a blockchain system, comprising:

one or more processors; and

a memory comprising instructions stored thereon, which when executed by the one or more processors, causes the one or more processors to perform:

receiving a proposed block on a first blockchain, the proposed block including (i) a latest secondary-chain block height and (ii) an epoched secondary-chain block height associated with a second blockchain;

determining whether the proposed block seals a current epoch by comparing a timestamp of the proposed block with an epoch duration threshold;

in response to determining that the proposed block is a sealing block of the current epoch:

(i) assigning a next block an updated epoched secondary-chain block height equal to the latest secondary-chain block height included in the sealing block, and

(ii) advancing to a next epoch;

in response to determining that the proposed block does not seal the current epoch, assigning to the next block the epoched secondary-chain block height included in the proposed block; and

verifying one or more messages included in the next block using a validator set obtained from the second blockchain at the epoched secondary-chain block height assigned to the next block, wherein all blocks within an epoch are verified against a same validator set.

12 . The system of claim 11 , further comprising stored sequences of instructions, which when executed by the one or more processors, cause the one or more processors to perform identifying the latest secondary-chain block height, the epoched secondary-chain block height, an epoch number, a minimum epoch duration, and an epoch start time from a block header of the proposed block.

13 . The system of claim 11 , wherein the epoch duration threshold is computed as an epoch start time plus a minimum epoch duration parameter defined by a virtual machine associated with the first blockchain.

14 . The system of claim 11 , further comprising stored sequences of instructions, which when executed by the one or more processors, cause the one or more processors to perform monotonically increasing, for each newly proposed block, a latest secondary-chain block height pointer corresponding to a most recent secondary-chain block height observable by the first blockchain at a timestamp of the newly proposed block.

15 . The system of claim 11 , wherein the sealing block is included in the current epoch and the next block is included in the next epoch.

16 . The system of claim 11 , further comprising stored sequences of instructions, which when executed by the one or more processors, cause the one or more processors to perform obtaining, at a block height corresponding to the epoched secondary-chain block height, a validator set recorded on the second blockchain.

17 . The system of claim 11 , wherein the latest secondary-chain block height is set by a block builder.

18 . The system of claim 11 , wherein advancing to the next epoch further comprises stored sequences of instructions, which when executed by the one or more processors, cause the one or more processors to perform:

incrementing an epoch number; and

assigning the incremented epoch number to the next block.

19 . The system of claim 11 , further comprising stored sequences of instructions, which when executed by the one or more processors, cause the one or more processors to perform:

prefetching, using a single lookup operation, of a next validator set from the second blockchain at the updated epoched secondary-chain block height assigned to the next epoch;

storing the next validator set for a duration of the next epoch; and

verifying blocks proposed for the duration of the next epoch using the stored next validator set.

20 . A non-transitory computer-readable storage medium comprising instructions stored thereon, which when executed by one or more processors, cause the one or more processors to perform operations for verifying messages in a blockchain system, comprising:

receiving a proposed block on a first blockchain, the proposed block including (i) a latest secondary-chain block height and (ii) an epoched secondary-chain block height associated with a second blockchain;

determining whether the proposed block seals a current epoch by comparing a timestamp of the proposed block with an epoch duration threshold;

in response to determining that the proposed block is a sealing block of the current epoch:

(i) assigning a next block an updated epoched secondary-chain block height equal to the latest secondary-chain block height included in the sealing block, and

(ii) advancing to a next epoch;

in response to determining that the proposed block does not seal the current epoch, assigning to the next block the epoched secondary-chain block height included in the proposed block; and

verifying one or more messages included in the next block using a validator set obtained from the second blockchain at the epoched secondary-chain block height assigned to the next block, wherein all blocks within an epoch are verified against a same validator set.