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I know that if Alice and Bob both have secret-public key pairs, they can use RSA for example. If we remove the possibility that Alice can know anything which Eve doesn't (ie Alice's secret key), is there an algorithm which makes encryption still possible?

(I am new in the topic and haven't been able to find an answer.)

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  • $\begingroup$ Are you asking that, if Alice doesn't know the public key of Bob and they didn't have a pre-shared secret key beforehand, can Alice send a secure message to Bob? $\endgroup$ – kelalaka Feb 29 at 20:48
  • $\begingroup$ Alice can know Bob's public key, she just cannot hide anything from Eve, for example her secret key, if the algorithm they were using was RSA. Yep, they don't have pre-shared secret key (because Eve would know it if Alice had it). Yes, I'd like to know if Alice can still send a secure message to Bob. $\endgroup$ – zabop Feb 29 at 20:51
  • $\begingroup$ That is how public key is working. Can we call this dupe of this How does asymmetric encryption work? $\endgroup$ – kelalaka Feb 29 at 20:59
  • $\begingroup$ Oh yes. Thank you! $\endgroup$ – zabop Feb 29 at 21:04
  • $\begingroup$ @zabop: can still send a secure message - What is secure for you? Alice can encrypt the message and only Bob can decrypt it, nobody else can decrypt it. In this sense it is secure. But in your case Bob does not know who sent this message. Eve can also encrypt any message and sent it to Bob and she can claim she is Alice. If Bob trusts any such message, this is not secure. $\endgroup$ – mentallurg Mar 1 at 11:25

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