A private key is created during asymmetric-key encryption, as part of public key cryptography. The private key is used to decrypt a message and transform it to a readable form. The private key is a matching, but different, key to the public one. Public and private keys are paired for secure communication, such as email communication. Keys are tiny bits of code that set off algorithms for text encryption and decryption.
A private key is only shared with the key's initiator, which ensures security. For example, A and B are message sender and message recipient, respectively. They have their own public and private keys pair. A, the message initiator (sendor), sends B a message. A's message is encrypted with B’s public key, while B uses its own private key to decrypt A’s received message. Digital signature (digital certificate) is used to make sure that A is the original message sender. B verifies that fact using the following steps:
In short, sending messages for encryption involves that sender uses recipient's public key and for encryption of digital certificate it's own private key. At the recipient end for decrypting message, recipient uses its own private key, while for digital certificate decryption, sender's public key is used.
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