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If you aren't worried about collusion or dynamic group membership, then a very simple solution is to simply have one key for encrypting the messages and another for signing them. The encryption key gives someone read access and the signing key gives them write access. Only nodes with the encryption key will be able to successfully decrypt the messages and ...


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You're confused about a few different things here. Assume that you have some cryptographic concept and you need to write down a definition of security. Such a definition can typically be written down as a game. When you write down your definition, you consider what the adversary should be able to do, i.e. it's while writing down the game that you assume ...


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Some observations, though I would recommend against inventing your own protocol, at least for real world use: When a new Chat group is formed, a random AES Key is generated and encrypted using each users public key. This means the protocol lacks forward secrecy. Anyone who compromises the private key of a chat participant can decrypt any previous chats ...


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How do I deal with user changing password (The key will be generated from password.)? Generate a random master key K. Use K to encrypt the files. Use the user's password to generate a second key, K'. Encrypt the master key using K'. Then when the user changes his password, all you need to do is decrypt the master key using the old password and re-encrypt it ...



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