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Public-key cryptography, or asymmetric cryptography, is the field of cryptographic systems that use pairs of related keys. Each key pair consists of a public key and a corresponding private key . [ 1 ] [ 2 ] Key pairs are generated with cryptographic algorithms based on mathematical problems termed one-way functions .
Asymmetric keys differ from symmetric keys in that the algorithms use separate keys for encryption and decryption, while a symmetric key’s algorithm uses a single key for both processes. Because multiple keys are used with an asymmetric algorithm, the process takes longer to produce than a symmetric key algorithm would.
Asymmetric encryption expands on symmetric encryption by incorporating two different types of keys into the encryption method: private and public keys. [20] A public key can be accessed by anyone and is unique to one user whereas a private key is a secret key that is unique to and only known by one user. [21]
Symmetric-key cryptography, where a single key is used for both encryption and decryption. Symmetric-key cryptography refers to encryption methods in which both the sender and receiver share the same key (or, less commonly, in which their keys are different, but related in an easily computable way).
Symmetric-key encryption: the same key is used for both encryption and decryption. Symmetric-key algorithms [a] are algorithms for cryptography that use the same cryptographic keys for both the encryption of plaintext and the decryption of ciphertext. The keys may be identical, or there may be a simple transformation to go between the two keys. [1]
Historically, before the invention of public-key cryptography (asymmetrical cryptography), symmetric-key cryptography utilized a single key to encrypt and decrypt messages. For two parties to communicate confidentially, they must first exchange the secret key so that each party is able to encrypt messages before sending, and decrypt received ones.
As a response, restrictions on symmetric keys were enhanced to be greater in size. Currently, 2048 bit RSA [8] is commonly used, which is sufficient for current systems. However, current key sizes would all be cracked quickly with a powerful quantum computer. [citation needed] “The keys used in public key cryptography have some mathematical ...
Public-key encryption was first described in a secret document in 1973; [14] beforehand, all encryption schemes were symmetric-key (also called private-key). [15]: 478 Although published subsequently, the work of Diffie and Hellman was published in a journal with a large readership, and the value of the methodology was explicitly described. [16]