Upgrading to a quantum resistant signature scheme influences the performance of the blockchain.
Now there are two types of speed that are influenced and are both important for the performance of the blockchain:
- Capacity, so the amount of transactions a blockchain can confirm in a second at maximum capacity. So if BTC for example can confirm 7 transactions a second (it’s max capacity), then as soon as more than 7 transactions per second are added to the network, BTC has reached its maximum capacity. In that case, the individual transactions will need to wait in line and the individual transaction speed is slowed down. (Unless you increase your fee, then your transaction will be prioritized and you might make the standard individual transaction speed. Of course depending on the height of other fees.)
- Individual transaction speed. This is the time within which you send a transaction and your transaction is confirmed on the network. This is the speed that applies for the moment where the blockchain is operating under its maximum capacity. So that means a transaction is added to a block almost as soon as it arrives at a node and gets processed right away.
The capacity depends on the block time (the amount of time it takes for a block to be mined) and the amount of transactions that fit in a block. The bigger the signature, the bigger and “heavier” the transaction, which results in either fewer transactions fitting in one block or bigger block size. Which in turn then results in less transactions confirmed per block or bigger block times which both leads to less transactions per second.
Now there could be solutions for the big signature size issue. Solutions being developed right now for scaling, could solve the problem for quantum resistant blockchains. But this is ongoing research to be looked into more in depth.
To overcome the shortfalls of post-quantum signature schemes some developers may decide to roll their own crypto, which has majorly failed in the past with other projects. Cryptography is difficult to understand and implement, much less post-quantum cryptography. Besides that it has to be tested and checked, preferably by external, professional parties to be proven secure. To this end there are only a handful of researchers worldwide even qualified in this specialty field. The NIST approval takes around 5 years of open source research. Self fabricated quantum resistant signature schemes ar a slippery slope.
In the next article, I will discuss the challenge of the human factor and lost addresses. You can continue reading part 5A here.