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These scheme doesn't really make sense in its current form: The key depends on the message. That means, it can not be chosen before the message is chosen. And it is't independent of other parts. How does the recipient receive that key? Or does he learn that from a separate communication channel, after the message (and thus the key) has been chosen? In that ...


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As an addition to the other answers: there are indeed multiple solutions available to you that do not rely on designing your own encryption-scheme and code. This is of importance as it is very easy to make mistakes on both the scheme and the implementation level. You might for example be able to take a certain (trusted) algorithm which should be safe and ...


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As no particular attack scenario has been given I'd add another, more high level option. When point-to-point transport security isn't supposed to be secure enough then you might consider end-to-end message security or application level security as well. The idea of TLS is that it protects messages from client to server. However, the client and the server ...


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Your idea lacks forward secrecy, which protocols like TLS often (in newer versions anyway) offer. Otherwise it is close to how such things are usually done. To get forward secrecy you would instead use an ephemeral Diffie-Hellman key exchange, which you would authenticate with the pre-shared public key (which would be a signing key, not an encryption key, ...


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This type of problem is known as anonymizing data, and it has fairly standard solutions. The obvious way is to use a Format Preserving Encryption method; that is a secret key method that has a fairly arbitrary domain. Because Alice is the only one who needs to be able to encrypt and decrypt, she can generate the key locally, and never distribute it. If we ...



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