The public key can be made available and used by anyone who will be sending messages to party number one. When party one receives messages encrypted with one's public key, then only party one will be able to decrypt, or read the message. At some point in the future, public keys will probably be published in a directory. In order to send an encrypted to message to someone else, their public key will be located and used to encrypt the message. The biggest drawback to public key encryption is the length of time that it takes to encrypt and decrypt messages.
Symmetrical encryption is much faster.
As a result, some messages may only need a digital signature encrypted with public key encryption, and the rest of the message can be sent as is or encrypted with more conventional encryption. The digital signature security feature that is available to public-key systems is digital hashing. Digital hashing transforms a message into a unique pattern of bits, called a digital signature. The original message cannot be decoded from the hash and any attempt to do so will change the digital signature. This protection ensures that a message cannot be changed in transmission without detection.