c# - Encrypt from server, decrypt on client (but not encrypt on client)? -

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is there way server can provide encrypted string can decrypted on client, not re-encrypted on client? know seems kind of backwards... here's need is.

i have software key needs activated against our remote server. server needs provide client says "you active" , contain info such date it's valid until, how many licenses, etc. however, need prevent being tampered increase license count or dates (i.e, re-encrypt value new date using key found in de-compiled binary or w/e).

is such thing possible using public/private keys? or perhaps hashes?

edit

alternatively, can server provide hash client can validate server without giving client ability spoof or generate hash on it's own?

thanks in advance.

public/private key encryption should need. hashes 1 way functions; hash function make impossible retrieve original value.

in case, server has public/private key pair , client has public/private key pair. server's public key embedded client, , server has client's public key well. server can encrypt payload using it's private key , client's public key. when client wants decrypt payload, uses it's private key , server's public key. client cannot re-encrypt data without access server's private key.

http://en.wikipedia.org/wiki/public-key_cryptography - explanation of how works

http://msdn.microsoft.com/en-us/library/e970bs09.aspx - starting point .net classes make easier


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