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Comment by deckar01 | Hacker News Reader

I'm not sure this warrants a patent. Upon further inspection the only real transformation they add to the Collatz function is returning the result modulo some prime. This is a very generic operation that can turn any function into hash-like mapping on a finite field.

They even had the nerve to include a generalization of the Collatz function in the patent.

> The hash function can apply more complex variations, such as adding multiplication, addition, modulo or other operation(s) in the even and/or odd operations.

With this generalization one can accidentally construct a variation that simplifies to an existing hash function (prior art?).

Should a patent really be allowed to control the use of an entire class of functions?

How can a patent claim ownership of an infinite number of transformations on an idea?

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The only thing you should read when evaluating the scope of a patent or patent application is the claims. In this case, the first claim is:

1. A method comprising:

receiving an input value and an iteration value;

based on the iteration value, iteratively performing steps comprising:

if a least significant bit of the input value is 0,

(1) dividing the input value by a first value,

if a least significant bit of the input value is 1,

(1) multiplying the input value by a second value,

(2) adding one to the input value, and

(3) applying a modulo operation of a prime value to the input value, to yield a first iteration value,

to yield an updated input value;

returning the updated input value as a hash value.

Note that the "first value" and "second value" can be numbers other than 2 or 3. Not even sure how that works.

Also, as the claim is currently written, it seems indefinite, or at least incorrect, because it is unclear if the modulo In step (3) is applied to the input value, or input value + 1, or the input value * second value, or (input value * second value) + 1. An exact reading of the claim implies the former, whereas what they probably want is the latter.

I'm not an expert in either of these areas - but how is cryptographic hashing an obvious application of the Collatz function? Is there some well-known property of Collatz sequences that make them suitable for crypto hashes?

This claim would probably also run into issues regarding patentable subject matter post-Alice v CLS Bank. It's almost completely abstract...

edit: nevermind, it's a patent application and not an issued patent.

HN Posters: Please stop posting patent applications as patents! They are not the same!

Cryptographic hashes have many different properties that make them useful and distinct. The most fundamental properties the Collatz function shares with hash functions include it being deterministic and non-invertable. Applying the modulo operation to map the input/output to a finite field provides uniformity. Change the function to b^k and you have the discrete logarithm problem.

Thanks for the simple yet clear explanation.

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