Hi This may be a double post if it is I apologise (I think I may have posted this before I was authorised by majordomo).
I have started using encryption and thought I would try this out. My question(s) are as follows - please be gentle 1: How is the IV handled in (AES) encryption - I can see supplying an initial vector is good but it also appears this should change with every encryption (if you like). So does a user have to know this + key ? 2: Is it possible to alter a key size say I am using SHA256 and want to output a SHA256 hash of a users password to use as a key ? Also can I pass something to openssl to get a hex digest ? 3: If a cracker can only retrieve 1 part of an encrypted file that has been deliberately split up - would having this 'part file' help or hinder the task of decrypting the contents of that file. 4: Is there a way that when attempting to decrypt a file you cannot know if you have been successful, i.e. you don't know the contents and try a key - you get an output from the attempt but it is not obvious if that output is correct (i.e file encrypted multiple times) or do all the encryption algorithms give a pass or fail or empty output. (i.e I tell you my pass-phrase is X and you use this to get output Y but you don't know what output Y is [could be further encryption], can you tell just be running the decryption algorithm that the key was a valid key?) I know this is a bit much for a first question but I am researching a lot and it is fairly new (but hopefully I am a quick learner). David
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