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What is Public Key Cryptography? (And How it Works)

by Nate Lord on Saturday May 6, 2023

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Learn how public key cryptography works as well as common uses for this cryptographic method.

What is Public Key Cryptography?

Public key cryptography (sometimes referred to as asymmetric cryptography) is a class of cryptographic protocols based on algorithms. This method of cryptography requires two separate keys, one that is private or secret, and one that is public. Public key cryptography uses a pair of keys to encrypt and decrypt data to protect it against unauthorized access or use. Network users receive a public and private key pair from certification authorities. If other users want to encrypt data, they get the intended recipient’s public key from a public directory. This key is used to encrypt the message, and to send it to the recipient. When the message arrives, the recipient decrypts it using a private key, to which no one else has access.

The Rivest-Sharmir-Adleman (RSA) algorithm is the cryptography system that is used for public key cryptography, which is commonly used when sending secure, sensitive data over an insecure network like the internet. The RSA algorithm is popular because it allows both public and private keys to encrypt messages so their confidentiality and authenticity remain intact.

Challenges of Public Key Cryptography

Speed often is cited as the most common challenge associated with public key cryptography. Several private key cryptography methods are a great deal faster than the public key encryption method that currently is available. One way of overcoming this challenge with public key cryptography is to combine it with secret key systems to offer the security advantages of the public key system and the speed of the secret (private) key system.

Another challenge associated with public key cryptography is that it has been susceptible to attacks through spoofed or compromised certification authorities. When these attacks take place, cyber criminals impersonate nearly anyone by choosing a public key certificate from the compromised authority. This allows cyber criminals to connect a public key to the name of another user.

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Benefits of Public Key Cryptography

The increased data security provided by public key cryptography is its main benefit. Public key cryptography remains the most secure protocol (over private key cryptography) because users never need to transmit or reveal their private keys to anyone, which lessens the chances of cyber criminals discovering an individual’s secret key during the transmission.

Public key cryptography also provides digital signatures that cannot be repudiated. Public key cryptography requires each user to be responsible for protecting his private key, whereas private key systems require users to share secret keys and perhaps even trust third parties for transmission. With the secret key system, it is possible for senders to claim the shared secret key was compromised by one of the parties involved in the process.

Public Key Cryptography vs. Private Key Cryptography

Public key cryptography is not intended to take the place of private key cryptography; it is to be used as a supplement to the secret key systems. That being said, there are some instances when private key cryptography is not ideal and public key cryptography becomes essential, especially in situations with large numbers of users. Typically, public key encryption is the cryptography method of choice when there is a multi-user environment and it is necessary to ensure confidentiality through key distribution and digital signatures for verifying user identities.

Public key cryptology has an advantage over symmetric private key encryption systems because it circumvents the logistics and risks inherent to secretly swapping keys. Due to its scalability and heightened security when compared to private key cryptography, public key cryptography remains highly popular and is widely used in enterprise environments today.

Tags:  Data Protection 101

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