Q: 1
What is the name of a one way transformation of a string of characters into a usually shorter fixed-
length value or key that represents the original string? Such a transformation cannot be reversed?
Options
Discussion
A . DES sounds tempting but it's reversible, unlike a hash. Some folks mix up substitution here but that's definitely not one-way.
Option A
Could be B here since DES is a well-known string transformation too, and it outputs a fixed length. I know DES is encryption so you can reverse it with the key, but the question wasn't super clear on reversibility for me. If I'm missing something obvious let me know.
Probably A since hashes are one-way and the others can actually be reversed.
A, but I always second guess when they mention "cannot be reversed" since some ciphers confuse me on wording.
Yeah, I'm thinking A fits best here since hash functions are explicitly one-way, can't go back to the source even if you try. C and D (transposition and substitution) are both forms of cipher that can usually be reversed with the right info. Not totally sure if I'm missing a use case though.
C/D? If the hash output length was longer than input, would that flip things?
Why are so many picking D? Isn't substitution usually reversible if you know the system, unlike a one-way hash?
D . Substitution makes sense to me since it's a way of transforming characters and sometimes results in a different string. The question just says the output can't be reversed, and basic substitution methods can get complex enough that reversing isn't practical. Not sure if that's exactly what they want here, but that's how I read it. Anyone see it differently?
Had something like this in a mock exam, it's A. One-way hash is designed to be irreversible, just like the question says. B (DES) can be decrypted if you have the key, so it doesn't fit here. Open to correction but pretty confident.
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