Summary

Key takeaways

Quantum computing poses a serious threat to public-key cryptosystems because their underlying mathematical problems can be solved efficiently with the help of quantum computers by using Shor’s algorithm. As a consequence, all present cryptographic signature schemes in use would be broken by a large-scale quantum computer once it’s available. Grover’s algorithm may also affect symmetric cryptoschemes and hash functions, but this could be overcome by increasing the key sizes or the length of the message digest, respectively.

What’s next?

Recent advances in the field of quantum computing may unsettle blockchain technologies in the near future. We’ll estimate the consequences of quantum computers for Bitcoin in the next chapter, “Bitcoin Under Broken Crypto Primitives." We’ll then introduce some cryptographic approaches that are considered to be secure in the post-quantum era in the chapter “Post-Quantum Blockchains.”