Nine Years to Halve a Hash Function: RFC 9861 Is Out

After nearly a decade in the making, RFC 9861: KangarooTwelve and TurboSHAKE was officially published in October 2025, with zkSecurity among its editors. This post explains why these hash functions deserve to be far more widely used than they are today. Built on the same Keccak permutation as SHA-3 and SHAKE but with the round count halved, they do the same job at the same security level roughly twice as fast. We cover why halving the rounds is safe, what the RFC actually defines, the caveats around FIPS compliance and workload-dependent speedups, and why a standard like this took nine years to land.