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I'm writing a program that needs to receive an encrypted message from the server and decrypt it on the client.
The problem in this case, is to prevent the client from being able to re-transmit messages encrypted with same key. RSA is designed to use the public key for encryption and private key for decryption. So if a client can decrypt a message (using private key), the client is also able to encrypt another message using it.
I know that it is possible to sign a hashed message using private key and then verify it using public key. But my scenario is not a digital signature problem. I just need a "read only" encryption.
Is it possible to do this using
RSA or any other asymmetric encryption algorithm?
I know that
RSA cannot encrypt data longer than it's key size and this is the reason for hashing data to a fixed length data. My supplemental question is: Can we convert a long message to a few small and fixed length blocks and use the same algorithm used in signing and verification to do encryption and decryption?