# Tag Info

### Why does the FBI ask Apple for help to decrypt an iPhone?

I'll try to take a stab at this. From Apple's iOS Security Guide, we learn that The metadata of all files in the file system is encrypted with a random key, which is created when iOS is first ...
Accepted

• 13.5k
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### Deterministically generate a RSA public/private key pair from a passphrase (with sufficient entropy)?

Yes, it is possible to deterministically generate public/private RSA key pairs from passphrases. For even passable security, the passphrase must be processed by a key-stretching function, such as ...
• 125k
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### Questions about the argon2 options

The entire point of a key-derivation function like Argon2 is to increase the time (difficulty) it takes to create a key, and as a side effect, increase the resources required to attack the key. The ...

### Why does Signal repeatedly hash the secure passphrase?

Am I correct in assuming that this does not add any extra security? No. This does add security and is a standard practice when dealing with passwords. What they do there is called a password hashing ...
• 44.7k
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### Relationship between PRF/KDF/MAC?

A key derivation function (KDF) takes in some secret keying material, which may or may not be uniformly distributed, and where the adversary may also have some auxiliary information about the keying ...
• 2,585