From the course: CISSP Cert Prep (2021): 3 Security Architecture and Engineering

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Hash functions

Hash functions

- [Instructor] Hash functions are extremely important to the use of public key cryptography. And in particular, to the creation of digital signatures and digital certificates. Let me start by giving you the technical definition of a hash function, and then I'll explain it to you, piece by piece. A hash function is a one-way function that transforms a variable length input into a unique fixed length output. Now let's pick apart that definition. Hash functions are one-way functions. That means that you can't reverse the process of hashing. If you have content, you can use a hash function to calculate the hash value of that content, but you can't go the other way around. If you have a hash value, you can't use it to figure out the original text, unless you already have a copy of that text. Hash functions, map variable-length input to fixed-length outputs. That simply means that you can send input of any length to a hash…

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