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In this scheme , is confidentiality guaranteed? A sends to B an encrypted file which is encrypted by B's public key. Can you illustrate any variant, still RSA- based but also using symmetric cryptography (no pre-shared keys) and lowering CPU time?

closed as unclear what you're asking by Ayrx, Xander, Adi, GdD, TildalWave Jan 14 '14 at 16:52

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  • Is this some kind of homework? – qbi Jan 14 '14 at 15:01
  • No, i found it on previous exam questions . I' m trying to do some past exams and i didn't know how to answer. – Pari Jan 14 '14 at 15:07
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    The whole point of the exercise isn't for someone else to do it for you, you know: if you do not know the answer or do not understand the question, it means you need to go back to your learning material and study it again. – Stephane Jan 14 '14 at 15:31
  • Yes for sure, i'm doing so just wanted to have some ideas . As the topic we did in class about rsa was not a profound study i had no idea how to deal with a question like this at the exam . – Pari Jan 14 '14 at 15:38
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Encryption is about maintaining confidentiality so I daresay that if you encrypt then you maintain confidentiality.

The exam question you quote probably wants you to talk about hybrid encryption (use RSA to encrypt an AES key; use AES to encrypt gigabytes of data). Look it up !

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