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1

I want to make a few points in addition to @NeilSmithline's excellent answer. Taking a 256-bit random value and hashing it with SHA-256, the output will still have (roughly) 256 bits of entropy. I say "roughly" because it's an open problem whether SHA256 actually maps to every possible string on 256 bits - but for all practical purposes, it's close enough. ...


3

Yes. Salt is used to prevent precomputation attacks, but random 256 bit strings are too large for precomputation. Slow hash functions with many iterations are meant to slow down dictionary attacks, but random 256 bit strings are too big for a dictionary or for exhaustive testing. So a single SHA256 hash is secure for long, cryptographically secure random ...


2

The technical answer is actually "no, because SHA-256 with RSA-2048 Encryption is not a certificate hashing algorithm. However, SHA-256 is a perfectly good secure hashing algorithm and quite suitable for use on certificates, and 2048-bit RSA is a good signing algorithm (signing is not the same as encrypting). Using 2048-bit RSA with SHA-256 is a secure ...


2

If you do the hashing on the server side, the server (and an attacker with access to it) could read your cleartext password, correct. But hashing the password on the client does not really help if someone managed to get access to the server - because the attacker could easily alter the javascript source to get your password in cleartext or start ...


2

You may be able to compute a SHA256 of part1-part2, if you already knew SHA256(part1), and the value for part2. This relies on a vulnerability in the underlying method of hash construction SHA256 uses (https://en.wikipedia.org/wiki/Length_extension_attack). EDIT: To clarify the algorithm SHA256 will pad any input to a multiple of some given size. Soo ...


1

Finding the original contents won't be helped if you only have part of the hash value. You still have to try possible input strings until you get lucky, i.e. hit the exact right one. In all generality, you can see it in the following way: if working with a partial hash value helped, then any attack on a full hash value would start by truncating that hash ...



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