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The question is simple. A and B are two parties exchanging information. A has public key p1 and private key pvt1. We know p1 is open for all but pvt1 is not for any one. Now A encrypts file with pvt1 and sends to B. B has p1. B also has his pvt2.
To do a secure transfer of data A uses pvt1 on the file and sends it to B. Now can B decrypt the file with just p1? Does he not need pvt1 as well? Then how this pvt1 will be exchanged? Or if pvt2 is needed to decrypt the file then how do they create pvt1 and pvt2?
Ok. Let me rephrase. I send you data encrypted with pvt1 key. So how do you open this document? Without my pvt1 how can you open? If you can open with your pvt2 key then shouldn't there be a relationship between pvt1 and pvt2 key? Otherwise how can you open my document ?