What is Public Key Cryptography?

Public Key Cryptography (PKC) or Asymmetric Cryptosystems – ever heard about this cryptography (data encryption) method?

This cryptography method involves two non-identical, but mathematically linked keys. One key is used to encrypt the data and is termed the public key, whereas the other key is used to decrypt the data and is termed the private key.

The public key is shared amongst multiple users for encrypting the data. The private key on the other hand is secretly stored by the recipient of the data. The recipient can use this key to decrypt the information and read the message.

Asymmetric cryptography is more preferred in the modern era than symmetric cryptography, wherein only one key is used in the entire encryption and decryption process.

SSL Certificates & Public Key Cryptography:

Public keys are too huge and hence sharing them is a tough task, since they are difficult to remember. Hence, these keys are placed on SSL certificates, for secured communication as well as easy sharing.

The private key which is also named the secret key is never shared with anyone. Its either stored in the user’s operating system, any software, or any external hardware (USB token) and is used for decrypting the ciphertext.

PKC is mostly used in SSL/TLS (Secure Socket Layers/Transport Layer Security) certificates, which are issued by reputed Certificate Authorities (CA). When these security certificates are installed on the website, they show their presence in the form of HTTPS (hyper-text transfer protocol secure) in the URL and a padlock in the address bar.

Types of PKC Algorithms:

The RSA algorithm (Ron Rivest, Adi Shamir, and Leonard Adleman algorithm) is used in public-key cryptography. The main motto of this algorithm is to secure the data communication encryption and ensure data integrity and data confidentiality.
The DSA (Digital Signature Algorithm) is generally used for digital signatures.

Challenges of Public Key Cryptography:

There are a few challenges that need to be addressed in public-key cryptography.

The most basic challenge of PKC is the speed factor. Symmetric cryptography is quicker than asymmetric cryptography since the former uses a single session key for the whole encryption and decryption process. As far as asymmetric cryptography is concerned, the use of two keys makes this process a bit slow. If both the keys used in the process are combined to form a single secret key, the process can become speedy.
Another tough challenge of PKC is – what happens when SSL certificates are compromised? To avoid it, the certificate authority undertakes strong validation for approval and issuance of an SSL Certificate. Moreover, the SSL certificate should be renewed timely. Use the latest version of TLS and protect your private key.

Properties of Public Key Encryption:

Two keys are used to encode and decode the information.
The decryption key owned by each recipient is unique.
Public key authentication is pivotal to prevent spoofing by an intruder posing as a recipient.
A complex encryption algorithm is used to encrypt the data, thus preventing the intruder from decoding the ciphertext.
Though this intelligent cryptosystem uses mathematically linked keys, the private key can’t be structured based on the public key. Hence, if the public key is compromised, the data still stays secured and can’t be decrypted.
Any of the keys (public key or private key) can be used to encrypt and decrypt the data.

Uses of PKC:

The main motto of PKC is:

Digital Signatures:

Digital signatures are used to sign digital content. The content is signed using the user’s private key, and the same is verified with the user’s public key.

Encryption:

Encryption of content is done using the user’s public key and the same is decrypted using the user’s private key.

Benefits of Digital Signatures in Public Key Cryptography:

Since the private key is secretly stored with the recipient of the message, its access is restricted to a single individual. Hence, when documents or emails are digitally signed, they offer the below-mentioned benefits. They are:

Authentication:

The private key is accessed by a single person and hence when that key is used for digital signatures, the recipients are assured that the signature is authentic and valid.

Non-Repudiation:

Since one individual has access to the private key, which is used for signing, the concerned person cannot repudiate their signature.

Integrity:

The digital signature is proof of data integrity, i.e., it guarantees that the content is not altered and is in original form. In case of alteration of content, the digital signature will become invalid.

Security Benefits of Encryption:

When data or a message is encrypted, it turns into a non-readable format. Its benefits are:

Data Confidentiality:

The encrypted data can be decrypted with the corresponding private key only. Hence, only the intended recipient can view the data thus assuring data confidentiality.

Data Integrity:

Before the content is decrypted, the contents are verified to ensure the originality of the content. Any modification in the original content may trigger an SSL error and the decryption process will fail.

Weaknesses of Public Key Cryptography:

Public Key Encryption is susceptible to brute force attacks. However, the use of strong and lengthy keys brings a hard time for hackers to crack it.
When the private key is lost, this cryptography method becomes unsafe.
This encryption is also susceptible to man-in-the-middle (MITM) attacks wherein an intruder can derange the communications by modifying the public keys.
If by chance, the private key is compromised, the entire network is at the risk of a cyber breach.

Public Key Cryptography Vs Private Key Cryptography:

Both cryptographic methods have their own set of advantages and disadvantages.

There have been cases wherein public key cryptography has an upper hand over private key cryptography, specifically when multiple users are involved.

This cryptography method is friendly for multiple users. Another advantage of asymmetric encryption (PKC) is that it evades the risks of key swapping.
Its scalability and robust encryption security make it more desirable and demandable in the digital market as compared to private key cryptography.
PKC also helps in maintaining email privacy as well as secured communications between the client and the server. It also helps in securing data stored on mail routers.
PKC comprises a DSA element that validates the private key which in turn validates the originality of the message and the sender.
Data confidentiality, authentication, and data integrity are the key benefits of PKC. These benefits help in enhancing user assurance about the authenticity of the message.
As stated before, public-key cryptography works more leisurely than symmetric cryptography since it uses huge keys and large numbers.
Since an extensive range of encryption keys are utilized in the PKC process, the security is more robust. This leads to minimum breaches and unauthorized intrusions.

Wrapping Up:

Though public key encryption involves risks wherein any hacker can compromise the SSL certificate on the site or the public key to penetrate networks, it still is the most ideal security solution.

As far as the speed factor is concerned, nowadays modern SSL/TLS certificates use both symmetric and asymmetric cryptographic methods to secure the web with their robust encryption and authentication.

Recommended Reading :