Question

Assymmetric Encryption: Why can a message encrypted with the Public Key only be decrypted with the receiver’s appropriate Private Key?

(a) Not true, the message can also be decrypted with the Public Key

(b) A so called “one way function with back door” is applied for the encryption

(c) The Public Key contains a special function which is used to encrypt the message and which can only be reversed by the appropriate Private Key

(d) The encrypted message contains the function for decryption which identifies the Private Key

I got this question in an internship interview.

This key question is from Encryption and Its Applications topic in portion Database Programming Techniques of Database Management

Answer 1

Right answer is (b) A so called “one way function with back door” is applied for the encryption

Best explanation: An one-way function is a function which a computer can calculate quickly, but whose reversal would last months or years. An one-way function with back door can be reversed with the help of a couple of additional information (the back door), but scarcely without this information. The information for the back door is contained in the private Key.