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What is Public Key Encryption?

  • Soumalya Bhattacharyya
  • Nov 24, 2022
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When two parties interact with one another to transfer data, the comprehensible or understandable communication, known as plaintext, is changed into what appears to be random nonsense known as ciphertext for security reasons.


Encryption describes the process of converting plaintext into ciphertext. Algorithms and keys are the two components of the encryption process. The plaintext-unrelated key is a value. The ciphertext can be communicated once it has been created. Depending on the exact key being used, the encryption technique will provide a different result. The algorithm's output varies when the key is changed. 


The ciphertext can be communicated once it has been created. When received, the ciphertext may be converted back to the original plaintext using the same encryption key and a decryption technique.


Asymmetric cryptography uses two sets of keys for encryption and decryption: a public key that is known to everyone and a private key (Secret key). Public key encryption is the term used for this.


With a pair of keys—one for encryption and the other for decryption—one algorithm is used for encryption and a related algorithm is used for decryption. The matching pair of keys must be held by both the Sender and the Receiver (not identical). One of the two keys has to remain a mystery. It is incredibly difficult to decode the message if one of the keys is kept a secret. It must be impracticable to figure out the second key without knowledge of the method, one of the keys, and samples of the ciphertext.


Also Read: What is Data Encryption? Examples and Types


What is Public Key Encryption?


Using two separate keys to encrypt or sign data, public key encryption makes one of the keys—the public key—available to everyone for usage. The private key is the name given to the other key. Only the private key may be used to decode data that has been encrypted using the public key. Public key cryptography is also referred to as asymmetric cryptography as a result of the usage of two keys as opposed to one. It is frequently used, particularly for TLS/SSL, which enables HTTPS.


Being able to just know the encryption key and cryptographic technique makes it impossible to figure out the decryption key, which is why encryption is crucial. It is possible to encrypt data using any of the two keys (public or private), and to decode it using a different key.


With the help of the public key cryptosystem, users now have a simple and practical way to encrypt data and validate digital signatures. Meanwhile, private keys may be kept private, guaranteeing that only the holders of the private keys have access to decode data and generate digital signatures.


RSA (Rivest–Shamir–Adleman) is the most extensively used public-key cryptography scheme. The foundation of RSA is how difficult it is to identify a composite number's prime components.


A pair of keys called a public key and a private key (a public key pair), which are connected to an entity that needs to electronically verify its identity or to sign or encrypt data, are used in public key cryptography. Every public key is made available, while the matching private key is kept hidden. Only the private key associated with the public key may be used to decode data that has been encrypted with it.


Both security and encryption are necessary for data. In addition to other things, encryption is essential for maintaining data security. It is the process of transforming data into an unreadable format that can only be deciphered or decrypted with the aid of a cryptographic key.


An encryption technique creates a random string of characters known as a cryptographic key. It is applied during encryption to transform plaintext into ciphertext. To change the ciphertext into plaintext, you may either use the same key (symmetric encryption) or a new key (asymmetric encryption).


Real communication is concealed by encryption, which turns it into ciphertext and renders it unintelligible. One such approach to communication encryption is public key encryption. Imagine it like a lock that has two keys (public key and private key). Only the second key may be used to open it after the first key has been used to lock it, and vice versa.


Also Read: 8 Strongest Data Encryption Algorithms in Cryptography


Why is Public Key Encryption important?


Public key encryption, commonly referred to as public key cryptography, is a method that encrypts and decrypts data using two unique keys. One is the public key, which anybody may use to encrypt data, and the other is the private key, which can only be used by the initiator to decode data.


Asymmetric encryption, often known as public key encryption, is a common component of Transport Layer Security/Secure Sockets Layer (TLS/SSL), which enables Hypertext Transfer Protocol Secure (HTTPS).


Public key encryption includes the following elements:


  • Plaintext: Data that can be read and understood and is used as input for an encryption process.

  • Ciphertext: The output of encryption in a format that is incomprehensible

  • Private key: A secret code typically used to decrypt encrypted messages

  • Public key: Everyone may use it, and it's frequently employed to encrypt messages.


You can obtain the recipient's public key from a shared directory in order to send an encrypted message to them. Send a message encrypted with this key, and the receiver may decode it using their matching private key.


But if you encrypt a message with your private key, only your public key can be used to decode it, proving your identity to the recipient. Without physically locking and unlocking a communication, you may automatically perform encryption and decryption. Companies utilize encryption software to complete the procedure quickly and provide strong data protection.


Since no one's private key must be shared, public key encryption is a very safe encryption method that prevents private key leaking during transmission. It offers strong information security and safeguards your data from illegal access.


Public key infrastructure (PKI) is used in Internet communications to handle identification and security. The fundamental technology that powers PKI and provides data security via a variety of communication channels is asymmetric encryption, often known as public key cryptography.


On the other hand, symmetric encryption, commonly referred to as private key encryption, employs a single key for both encryption and decryption. Based on the use case and desired encryption strength, both symmetric and asymmetric encryption offer advantages and disadvantages.


Also Read: Symmetric vs Asymmetric Encryption


How does public key encryption work?


Users can transmit and receive communications covertly using public key encryption. It enables the creation of a public key and a private key for each user. There is a mathematical relationship between the two keys. However, it is not possible to practically create a private key from a public key.


A communication can be encrypted using a public key in encryption, which the recipient's private key can only decrypt. Additionally, if a communication is encrypted by the sender using a private key, the recipient can use a public key to confirm the sender's identity.


Longer key lengths are used in public key encryption, which eliminates the requirement for key exchange and lessens the difficulty of key management. A key cannot be used to decode a message after it has been encrypted using it.


Applications of Public Key Encryption:


E-signatures often employ public key encryption. A mathematical procedure known as an e-signature is used to verify a user's identity and uphold the integrity of a communication, document, or piece of software. E-signature software is typically used by businesses to distribute and gather digital signatures on legally important documents.


Public key cryptography is used for many more things besides digital signatures:

Applications of Public Key Encryption

Applications of Public Key Encryption


  1. Identity Authentication:


Identity security is essential for businesses since data has now spread outside of traditional networks and into the cloud, mobile devices, Internet of Things (IoT) devices, and other technologies. To avoid brute force attacks, companies can utilize digital identity certificates in place of passwords thanks to public key cryptography.


Also Read: Top 7 Identity Management Tools


  1. Securing a web server:


TLS/SSL, the encryption technology that assures security in HTTPS, is based on public key cryptography. It guards against online threats including man-in-the-middle attacks, which let a hacker intercept communications and read message content, and shields web servers and clients from online threats like these. 


A component of HTTPS is symmetric encryption, which uses symmetric encryption keys to carry out the encryption process, and public-key encryption to exchange keys between two parties.


By allowing the sender and receiver to confirm their identities, public key encryption enables them to fend off man-in-the-middle assaults. In addition, web server security gives websites a boost in search engine rankings, such as Google or Bing.


  1. Email Privacy:


Public key encryption is used for email encryption to authenticate and encrypt messages. It aids in securing communication from harmful hackers or unauthorized parties. Due to encryption, even if an attacker manages to guess a mail server password, they won't be able to see the contents of emails.


By digitally signing emails to establish your identity and encrypting the text and attachments while they are in transit or being stored on a server, email encryption software can help you safeguard communications.


Public key infrastructure is used by secure email encryption techniques like secure/multipurpose internet mail extensions (S/MIME) certificates to validate digital identity and enable encryption.


  1. Cryptocurrency:


Public key cryptography is used for transactions in well-known cryptocurrencies like Bitcoin. Users have a public key that is visible to everyone and a private key that is used to complete a transaction that is kept hidden.


Unspent transaction outputs (UTXO), for instance, in the Bitcoin ledger are connected to a public key. User A creates a new UTXO connected to User B's public key and uses their private key to spend the original UTXO when User A and User B wish to sign a transaction.


Benefits of public key encryption:


Greater data security is the major benefit of adopting public key cryptography. It lessens the chance that a cybercriminal would intercept a private key and use it to intercept conversations by requiring users to not distribute, transmit, or divulge their private keys to anybody.


It aids users in overcoming key distribution difficulties associated with employing private key encryption. It lets businesses protect the confidentiality and integrity of their data, resulting in stronger information security.


Along with providing strong encryption, public key cryptography also enables users to confirm their digital identities and ensures non-repudiation. Asymmetric cryptography is a preferred kind of encryption as a result of these advantages.


Compared to symmetric cryptography, public key encryption uses two keys and is therefore safer. Public key encryption does not need the exchange of private keys, which removes the headache of key management. In contrast, symmetric encryption makes it possible for a stolen or misplaced private key to undermining the entire system.


Messages are encrypted using a complicated procedure called public key encryption. Although it requires more resources and time than symmetric encryption, it provides more security. Additionally, digital certificates are encrypted so that even if they are hacked, malevolent hackers cannot access them.


The type of encryption used will depend on the device's purpose, makeup, storage capacity, processing power, level of security, and other factors. Both symmetric and asymmetric cryptosystems will have benefits and drawbacks depending on these factors.




Every public key in public key encryption corresponds to a single private key. They function as a unit to encrypt and decode communications. If you use a person's public key to encrypt a message, they can only decode it if they have the corresponding private key.

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