Public and Private Keys
The private key is used in both encryption as well as decryption. This key is shared between the sender and receiver of the encrypted sensitive information. The private key is also called 'symmetric' because it is shared by both parties. Private key cryptography is faster than public-key cryptography mechanism.
A private key is generally a lengthy, non-guessable sequence of bits created randomly or pseudo-randomly. The complexity and length of a private key define how easy it is for an attacker to carry out an attack, in which they test out several keys until they find the appropriate one.
Asymmetric cryptography, often known as public-key cryptography, is a type of encryption that employs pairs of keys. A public key (which may be known to others) and a private key (which may not be known to anyone except the owner) make up each pair. Cryptographic techniques based on mathematical problems known as 'one-way functions' are used to generate such key pairs.
A private key should be kept secret for effective security, whereas a public key can be freely circulated without jeopardizing security.
In such a system, anybody can encrypt a message using the intended receiver's public key, but only the receiver's private key can decode the message. This allows a server application to produce a cryptographic key for compatible symmetric-key cryptography, then encrypt that freshly generated symmetric key using a client's public key.
A public-key encryption system's most apparent application is for encrypting communication to guarantee secrecy – a message that a sender encrypts using the recipient's public key and can only be decoded by the recipient's associated private key.
To conclude, private keys can be used for both encryption and decryption, while public keys are used only for the purpose of encrypting sensitive data. Private keys are shared between the sender and the receiver, whereas public keys can be freely circulated among multiple users.