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If plaintext $p$ is a variable with any distribution over $\{0,1\}^n$ and $k$ is an independent uniform random variable over $\{0,1\}^n$ then ciphertext $c = p ⊕ k$ is a uniform random variable over $\{0,1\}^n$.


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I am wondering if you have an input $x_{1}$ and you XOR it with an unknown random second input $x_{2}$, is it safe to say that the resulting $x_{1}\oplus x_{2}$ will be random ? Yes, this is literally what proofs of the security of one-time pads come down to. Informally it comes down to the following observations: If $x_2$ is random, then it means that ...


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Although it is not forward secure against client-side compromise (i.e. disclosure of the user agent's long term private key), it is forward secure against server-side compromise (i.e. disclosure of all information available to the server). Thus, for example, if ownership of the application server is transferred from one company to another and the user's ...


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Are there any cryptographic primitives/protocols allowing the sender to signal to the recipient faster that the message is intended for them, yet not reveal the true recipient to everyone else and allow them to quickly skip trying to decrypt the message? It doesn't appear that the problem of recognizing the message (without leaking who the message is for) ...


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How this general kind of thing is handled today is with hybrid encryption. A symmetric key is generated and the message is encrypted with that. Then the symmetric key is key wrapped (encrypted) using the public key of each intended recipient. (Keep in mind that RSA can only encrypt small amounts of data.) This only encrypts the data once. You can make it ...


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