October 5, 2018 Knowledge Center

What Is Symmetric and Asymmetric Cryptography?

As the threat of different types of cyber crimes becomes much more severe, information security becomes much more sophisticated. Cybersecurity experts continue to tighten communication security, leaving no loopholes that criminals could exploit later. One of these security schemes is asymmetric cryptography or encryption.

Asymmetric cryptography uses two keys – public and private, both of which are mathematically related and have a specific role in the operation. Data that is encrypted with a private key can only be decrypted with a public key and vice versa. You cannot encrypt and decrypt data using the same key.

The private key must remain private, or you will compromise the security of the whole system. In case the private key is breached, a new pair must be created.

Asymmetric encryption is far better than its symmetric counterpart at protecting information. Some of the uses of asymmetric cryptography are in DSA, elliptic curve technique, and PSA.

However, it is still not compatible with bulk encryption because it is much slower than symmetric cryptography.

How Does Asymmetric Cryptography Work?

Asymmetric encryption has a sender and receiver, both of whom receive a key set. In other words, each of them will have a private and public key. Before sending any data, the sender will first encrypt it using his private key. Once the receiver receives the information, he will decrypt it with his public key.

To utilize this type of encryption, a method should be used to discover public keys. One of these methods is the use of digital certificates within the client-server communication model. The certificate contains information, such as the email address and country of the user, the name of the organization, the organization that gave the certificate, the public key of the users, and any other information that will identify the server and the user.

When a client and a server need secure encrypted communication, both of them will send a query over the network to each other. Once they receive that, a copy of the certificate is sent back. The certificate contains the sender’s public key, which the receiver can use.

Asymmetric cryptography is an essential part of the blockchain, especially in the Bitcoin protocol and as proof of work in Bitcoin mining.
The Bitcoin protocol uses the Elliptic Curve Digital Signature Algorithm, or ECDSA, which is used to create a public and private key. These are used to make sure the digital transaction is legitimate.

In mining, those who mine use the “SHA256 Hash Function” to find the cryptographic nonce in a specific block before adding it to the blockchain. The number of zeros in each hash changes as they are inserted in the blockchain.

Asymmetric cryptography makes it difficult for anyone to change what has been already added to the blockchain.

Symmetric vs. Asymmetric Encryption

If asymmetric cryptography uses two keys, symmetric encryption uses only one key; thus, it has a more straightforward process. Both parties have one secret key which they use to code and decode the data they receive.

It has been the mode of encryption for a long time, but there are loopholes in the communication security causing the creation of asymmetric cryptography. Until now, symmetric encryption is still used primarily in the transfer of massive data.

Uses of Asymmetric Cryptography

Asymmetric cryptography has several practical applications in different business, but two of its primary purposes are for digital signatures and encryption.

Digital Signatures

In this application, the user digitally signs the content using his/her private key and verifies it with their public key. Digital signatures offer several benefits:

– Receivers are confident that the material comes from the sender himself since he only has access to his private key which he used to sign the document.
– Senders cannot repudiate later that they did not author or sign the digital document/content.
– Once the signature is verified, it checks whether the content of the information matched the exact content when the sender applied their signature. Any change done to the original, no matter how small it is, will cause the authentication to fail.


Information is encrypted using the user’s public key and can only be decrypted with their private key. Therefore, the sender is confident that only the receiver can view the information sent. They are also assured that they are receiving the original content because any slightest change done to the document after it was encrypted will cause the decryption to fail.

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