What is a private key?

Posted on October 28, 2022  •  2 minutes  • 396 words

What are private and public keys?

In cryptography, a private key is a piece of information that is used to encrypt and decrypt messages. It is a secret value that is known only to the person or entity that generated it, and it is typically used in combination with a public key to create a secure communication channel.

Private keys are an essential part of many cryptographic systems, including public-key cryptography and digital signature systems. In public-key cryptography, a private key is used to generate a digital signature, which is a mathematical value that is unique to the message being signed. This signature can then be verified using the corresponding public key, which is available to anyone who needs to verify the authenticity of the message.

Private keys are typically long, random, and unique strings of characters, and they are carefully guarded by the individuals or entities that use them. It is important to keep private keys secure, as anyone who has access to a private key can use it to decrypt messages or forge digital signatures.

Example

Here is an example of how private and public keys are used in public-key cryptography:

Alice wants to send a secure message to Bob, but they have never exchanged keys before. To do this, Alice uses a public-key cryptography system, which generates a pair of keys: a public key and a private key. Alice’s private key is kept secret, while her public key is shared with anyone who wants to send her a message.

Bob receives Alice’s public key and uses it to encrypt the message that he wants to send to Alice. He then sends the encrypted message to Alice.

When Alice receives the encrypted message, she uses her private key to decrypt it. Only Alice has access to her private key, so only she can read the message that Bob sent to her.

In this example, the private key is used to decrypt the message, while the public key is used to encrypt it. This allows Alice and Bob to communicate securely, without having to exchange keys in advance.

Final word

To summarize, private keys are used to decrypt messages and generate digital signatures, while public keys are used to encrypt messages and verify signatures. These keys are typically used together, with the private key being kept secret and the public key being shared with others.