reply on: I have been asked to ELI5 cryptographic hashes to kids (grade 8).. Is this ok? \ stacker news ~bitcoin

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0 sats \ 3 replies \ @02fa90fd41 OP 16 Jun 2023 \ parent \ on: I have been asked to ELI5 cryptographic hashes to kids (grade 8).. Is this ok? bitcoin

Thanks for the question, all questions help me perfect this. So ..

The code is a representation of the grade. So by looking at the code the teacher knows the grade for the student.

So for example

Locker	Grade	Grade (MD5 Hash)
1	C	0b90224d10e44e42f4891b2e5a2d4d16
2	A	7fc56270e7a70fa81a5935b72eacbe29
3	B	e9d71f5ee7c92d6dc9e92ffdad17b8bd

To anyone who does not know the code, they see the hash and have no idea what is happening. The teacher however knows the code and what grade they are linked to. The locker have names on. So the teacher can see that locker 1 (lets say john) has a grade of C

0 sats \ 2 replies \ @ek 16 Jun 2023

Ah, okay, now I see.

However, two things:

Any student with the same grade will have the same hash
A smart child may realize they can just put every grade into the Hasher machine and compare the hashes. This assumes that the Hasher machine is publicly accessible (which should be the case if you want to have a good analogy to hash functions).

Because of this, I would say this example is not a good use case for hashing, to be honest. Non-deterministic encryption with a secret key should be used here.

0 sats \ 1 reply \ @02fa90fd41 OP 16 Jun 2023

If you have any suggestions I would appreciate another analogy

10 sats \ 0 replies \ @ek 16 Jun 2023

You can fix your example by using salt || MD5(grade || salt || secret) as the code on the lockers.

salt is just a random value which makes sure that every hash will be different.

secret is a secret value which only teachers know. This prevents that students can just try every grade and compare hashes.

With || I mean concatenation.

This may be too complicated for 8 graders now though.