Encrypt file from sha512 hash?

Would like to know how to encrypt a file (lets say a .txt o开发者_如何学运维r .xml) with SHA512 hash ? How to proceed ?

What i would want to do is.. check if the file exist.. open it and then read it while unencrypting it.

Thanks!

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That is not possible. SHA512 is a hashing algorithm, not an encryption algorithm.

If you want to get the hash for a file, you can use the SHA512 class.

Example:

Dim data As Byte() = File.ReadAllBytes("file.txt")
Dim result As Byte()
Dim sha As New SHA512Managed()
result = sha.ComputeHash(data)

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A hash tells you the integrity of a series of bytes.

Encryption obscures or hides information.

To encrypt of file you could follow the MSDN tutorial:

http://msdn.microsoft.com/en-us/library/system.io.file.encrypt.aspx

Since you mention you want to do this 'on the fly', you could also select one of the .NET encryption algorithms and implement your own using the FileStream object:

http://support.microsoft.com/kb/307010

A google search reveals a wealth of information on the subject.