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21 sats \ 4 replies \ @ek 16 Jun 2023 \ on: I have been asked to ELI5 cryptographic hashes to kids (grade 8).. Is this ok? bitcoin
I would say: "not even the Hasher machine can decode"
I don't get this example. The code on each locker represents the student's grade? Isn't the code on their locker independent from any grade they get? I assume you are talking about a code which identifies that this is their locker?
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
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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.
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If you have any suggestions I would appreciate another analogy
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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.
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