Public key cryptography (PKC) also known as asymmetric cryptography is a framework that uses a public key and a private key as opposed to the single key used in symmetric encryption. The use of key pairs gives PKC a unique set of properties and capabilities that can be used to solve challenges inherent in other cryptographic techniques. This type of encryption has become an important component of modern computer security, as well as a crucial component of the emerging cryptocurrency ecosystem.
How does public key cryptography work?
In public key encryption, the public key is used by the sender to encrypt the information while the private key is used by the recipient to decrypt it. Because the two keys are completely different from each other, the public key can be securely shared without compromising the security of the private key. Each asymmetric key pair is unique, ensuring that a message encrypted with a public key can only be read by the person who has the corresponding private key.
Because asymmetric encryption algorithms generate mathematically related key pairs, their key lengths are much longer than those used in symmetric encryption. This length is usually between 1,024 and 2,048 bits. This makes it extremely difficult to compute a private key via its public counterpart. One of the most common algorithms for asymmetric encryption in use today is known as RSA. In the RSA scheme, keys are generated using a parameter arrived at by multiplying two numbers (often two large key numbers). In other words, the standard creates two keys (one public that can be shared and one private that must be kept secret). The RSA algorithm was first described in 1977 by Rivest, Shamir, and Adleman (hence RSA being the initials of each participant's name) and remains a key component of public key cryptosystems.
PKC as a cryptographic tool
Public key cryptography solves one of the long-standing problems of symmetric algorithms which is the key connection used for both encryption and decryption. Sending this key over an unsecured connection exposes it to third parties who can then read any messages encrypted with the shared key. Although there are cryptographic techniques (such as the Diffie-Hellman-Merkle key exchange protocol) to solve this problem, they are still vulnerable to attacks. In contrast, in public key cryptography the key used for encryption can be securely shared across any connection. As a result, asymmetric algorithms provide a higher level of protection when compared to symmetric ones.
Use it to create digital signatures
Another application of asymmetric encryption algorithms is authenticating data through the use of digital signatures. Simply put, a digital signature is a hash created using the data in the message. When this message is sent, the signature can be verified by the recipient using the sender's public key as a way to authenticate the source of the message and to ensure that it has not been tampered with. In some cases digital signatures and cryptography are applied together where the hash itself can be encrypted as part of the message. However, all digital signature schemes do not use encryption techniques.
Restrictions
Although it can be used to improve computer security and provide message integrity verification, public key cryptography has some limitations. Due to the complex mathematical operations involved in encryption and decryption, asymmetric algorithms can be rather slow when having to deal with large amounts of data. This type of encryption also relies heavily on the assumption that the private key will remain secret. If the private key is accidentally shared or exposed the security of all messages encrypted with the corresponding public key will be compromised. It is also possible for users to accidentally lose their private keys in which case it becomes impossible for them to access encrypted data.
Applications of public key cryptography.
This type of encryption is used in many modern computer systems to provide security for sensitive information. For example, electronic messages can be encrypted using public key encryption techniques to keep their contents confidential. The Secure Sockets Layer (SSL) protocol, which makes secure communications with websites, also uses an asymmetric encryption method. PKC systems have even been explored as a means of providing a secure electronic voting environment that would allow voters to participate in elections from their home computers.
Public key cryptography also features prominently in blockchain technology and digital currencies. When a new cryptocurrency wallet is set up, a pair of keys (public and private keys) are created. The public address is generated using the public key and can be securely shared with others. The private key, on the other hand, is used to create digital signatures and verify transactions and therefore must remain secret. Once the transaction is verified by confirming the hash in the digital signature this transaction can be added to the public blockchain ledger. This digital signature validation system ensures that only the person who owns the private key associated with a cryptocurrency wallet can release funds from it. It should be noted that asymmetric ciphers used in digital currency applications are different from those used for computer security purposes. For example, Bitcoin and Ethereum use specialized cryptography known as Curve Digital Signature Algorithm (ECDSA) to verify transactions.
From computer security to verifying cryptographic transactions, public key cryptography plays an important role in securing modern digital systems. Using paired public and private keys, asymmetric cryptographic algorithms solve the fundamental security issues presented by symmetric ciphers. Although public key cryptography has been in use for many years, new uses and applications are regularly developed for it. Especially in the field of blockchain and digital currencies.