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Home » Blog » Encryption » What Is a Public Key Cryptography and How Does It Work? 


APRIL 12 2023


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What Is a Public Key Cryptography?

Public key technology, also known as asymmetric encryption, is an essential aspect of modern security and encryption. It enables secure communication between two parties without sharing a secret key, making it a key component of online security. In this brief, we will explore the fundamentals of public key cryptography, its advantages, and how it differs from symmetric encryption. 

A Definition of Public Key Cryptography

Public key cryptography is based on the following principles:

  1. It is possible to generate a pair of very large numbers (public key and private key) so that knowing the public key it is impossible to calculate the private key in a reasonable amount of time. In this case, the generation mechanism is well known.
  2. Strong encryption methods are available to encrypt a message with the public key so that it can only be decrypted with the private key. The encryption mechanism is well known.
  3. The owner of two keys does not disclose the private key to anyone, but does share the public key with counterparties or makes it publicly known.


If it is necessary to transmit an encrypted message to the owner of the keys, then the sender must receive the public key. The sender encrypts his message with the recipient’s public key and transmits it to the recipient (the owner of the keys) over open channels. At the same time, no one can decrypt the message except the owner of the private key.

As a result, messages can be securely encrypted while keeping the decryption key secret for everyone – even the message senders.

This principle can be explained through the everyday analogy “lock – key to the lock” for sending a parcel. Participant A has a personal lock and a key to it. If participant A wants to receive a secret package from participant B, then he publicly gives him his castle. Participant B locks the lock on the secret package and sends it to participant A. Having received the package, participant A opens the lock with the key and receives the package.

Knowing about the transfer of the lock and intercepting the package will not give anything to a potential attacker: only participant A has the key to the lock, so the package cannot be opened.

How Does a Public Key Work?

Public key cryptography works with two different keys: public and private. The public key can be published and used to encrypt the message, while the private key is used to decrypt it. Encryption keys are used in the following processes:

  1. Key generation: Each user generates encryption key pair – public and private. The public key is distributed around the world, while the private key is kept secret by the user.
  2. Encryption: If user A wants to send a private message to user B, he uses user B’s public encryption key to encrypt the message. Only user B can decrypt the message with their private key.
  3. Signature: If user A wants to sign the document, he uses his own private key to create an electronic signature. Anyone with user A’s public key can verify the signature and verify the authenticity of the document.

Public Key Applications

Public key cryptography has a wide range of applications in data security. From secure online communication to digital signatures, public key encryption has revolutionized the way we transmit and store information. In this brief, we will explore some of the most common applications of public key cryptography, including secure messaging, secure browsing, and secure data storage.


Asymmetric encryption is a cryptographic technique that uses two different keys: public and private. This public key encryption method allows for secure transmission of data over open networks such as the Internet.

The public key is used to encrypt data and the private key is used to decrypt it. The public key can be freely distributed and used by any sender, while the private key must be well protected and available only to authorized users.

When the sender sends a message, it uses the intended recipient’s public key to encrypt the data so that only the recipient with access to the corresponding private key can decrypt the data. This prevents unauthorized access to data and ensures the confidentiality of information.

Digital Signatures

A digital signature is a method of verifying the authenticity of a message or document in electronic form. It is used to protect against forgery and alteration of information during transmission. A digital signature is created using public key algorithms, where the sender of the message uses their private key to create the signature, and the recipient uses the public key to verify the signature.

Digital signatures are widely used in many areas such as banking, healthcare, government organizations, and many others. This is because digital signatures ensure that information has not been tampered with or altered in transit. This allows you to maintain the integrity and confidentiality of data in the digital environment.

Key Exchange

Key exchange is the process of exchanging keys between two users, which is used to ensure the security of data transmission. This process uses asymmetric key encryption scheme to create a shared key that is used to encrypt and decrypt data. The key exchange may be performed using various protocols such as the Diffie-Hellman protocol or the RSA algorithm.

Key exchange is especially important in Internet security, where it is used to protect the confidentiality and integrity of data transmitted over open networks such as the Internet. Key exchange allows you to establish a secure communication channel between the sender and recipient, where data can be transferred without the risk of interception or modification by third parties.

Components of Public Key Encryption

The main components of public key encryption are the public and private keys. The public key is used to encrypt data and the private key is used to decrypt it. In this case, the public key can be distributed openly, while the private key should be known only to the owner.

Another important component is the digital signature, which allows you to verify the authenticity of the message and identify the sender. The digital signature is created using the private key and verified using the public key.

Asymmetric encryption is a secure way to transfer data, as it is almost impossible to break the public key encryption system. However, system reliability can be compromised if components are compromised or stolen.

Public Key Risks

One of the main risks of asymmetric encryption is the possibility of an attack on the private key. If an attacker gains access to a private key, he can easily decrypt all messages encrypted using the corresponding public key. This may lead to the leakage of confidential information or a breach of privacy.

Another risk is the possibility of a man-in-the-middle attack, where an attacker can replace the recipient’s public key with his own, allowing him to decrypt and intercept messages sent to the recipient.

Finally, asymmetric key algorithms can also be subject to man-in-the-middle attacks, where an attacker can intercept and modify messages sent between two users and compromise data protection.

Benefits and Drawbacks of Public Key Cryptography

One of the main advantages is the ability to securely transfer confidential information necessary to protect against unauthorized access and data leakage. In addition, public key cryptography lets users to create digital signatures to identify the sender and verify the integrity of the message.

However, public key cryptography also has disadvantages, such as high computational complexity, which can slow down the encryption decryption and encryption process. In addition, problems can arise if the private key is compromised, which can lead to a breach of data confidentiality.

Another disadvantage is the vulnerability to man-in-the-middle attacks, where an attacker can replace the recipient’s public key with his own, allowing him to decrypt and intercept messages sent to the recipient.

Comparison of Public Key Cryptography and Private Key Cryptography

Symmetric cryptography uses a shared secret key to encrypt and decrypt messages. This key must be known to both the sender and the recipient, which can be useful if the number of participants is small. However, in the case of a large number of users, the secret key exchange can be complicated and potentially insecure.

Asymmetric cryptography uses a public and private key pair to encrypt and decrypt messages, respectively. The sender uses the recipient’s public key to encrypt the message, which can then only be decrypted using the recipient’s private key. This allows for secure communication without requiring the exchange of a secret key.

Symmetric cryptography is usually faster and more efficient, but requires the exchange of a secret key, which can be vulnerable to attack. Asymmetric cryptography is more secure and convenient in case of a large number of users, but less fast and efficient.

The choice between symmetric and asymmetric cryptography depends on the specific situation and security requirements. In some cases, it may be better to use a combination of both methods to provide the best data protection.


Public key cryptography is one of the most important security technologies for sensitive information. Whether it’s digital signature, public key infrastructure, or private key encryption, both the public key encryption algorithms used and their implementation are important. Helenix has a unique experience in the implementation of public key systems in hardware and software-hardware form. You can learn more about our competencies in the Custom Development section.


Public key cryptography is an essential aspect of modern security, with RSA being a popular example. RSA uses a pair of keys, one for encryption and the other for decryption, to secure messages in transit and storage.

Cryptography is the practice of creating secure communications using techniques such as symmetric encryption, hashing, digital signatures, and asymmetric encryption. Methods such as RSA or Diffie-Hellman use a combination of these techniques to keep information secure.

The Diffie-Hellman key exchange is an example of a public key cryptography system that enables two parties to establish a shared secret key without directly transmitting it. By using a combination of private and public keys, this process is both secure and efficient.

A public-key cryptosystem uses a pair of keys – public and private – to encrypt and decrypt messages, providing secure communication between parties without the need for a shared secret key.