Mention support for collision-resistant PRFs

draft-lucas-balloon-hashing.md

@@ -149,7 +149,7 @@ informative:
 
 --- abstract
 
-This document describes Balloon, a memory-hard function suitable for password hashing and password-based key derivation. It has proven memory-hardness properties, is built from any standard cryptographic hash function or extendable-output function (XOF), is resistant to cache-timing attacks, and is easy to implement whilst remaining performant.
+This document describes Balloon, a memory-hard function suitable for password hashing and password-based key derivation. It has proven memory-hardness properties, is resistant to cache-timing attacks, is easy to implement, and is built from any collision-resistant pseudorandom function (PRF), hash function, or extendable-output function (XOF).
 
 --- middle
 
@@ -158,9 +158,9 @@ This document describes Balloon, a memory-hard function suitable for password ha
 Balloon {{BCS16}} is a memory-hard password hashing and password-based key derivation function that was published shortly after the Password Hashing Competition (PHC), which recommended Argon2 {{?RFC9106}}. It has several advantages over prior password hashing algorithms:
 
 - It has proven memory-hardness properties, making it resistant against sequential GPU/ASIC attacks. An adversary trying to save space pays a large penalty in computation time.
-- It can be instantiated with any cryptographic hash function or XOF, making it a mode of operation for these existing algorithms. No new, unstudied primitives are required.
+- It can be instantiated with any collision-resistant PRF, hash function, or XOF, making it a mode of operation for these existing algorithms. No new, unstudied primitives are required.
 - It uses a password-independent memory access pattern, making it resistant to cache-timing attacks. This property is especially relevant in cloud computing environments where multiple users can share the same physical machine.
-- It is easy to implement whilst being fast enough for real-world use.
+- It is intuitive to understand and easy to implement, which reduces the risk of implementation mistakes.
 
 Unfortunately, the paper did not fully specify the algorithm nor provide guidance on parameters. Furthermore, the algorithm was not designed with key derivation in mind and had multiple variants.