Asymmetric key cryptography uses a public key to encrypt text, which can only be decrypted by a private key. It allows secure communication without sharing secret information, but is slower and can potentially be cracked. It is the basis for tools like PGP, SSL, and TLS, and can guarantee confidentiality and authenticity. The strength of the encryption depends on the length of the keys and the difficulty of the math connecting them. The RSA algorithm is the most common, but key lengths must increase to ensure security against hackers.
Asymmetric key cryptography is the process of transforming text to hide its meaning using a shared public key. The text can only be decrypted by a secret private key that is different from the public key, but mathematically related. The primary uses of asymmetric key cryptography are symmetric key exchanges, certificate-based authentication, and digital signatures.
The advantage of asymmetric-key cryptography over symmetric-key cryptography, in which the same key is used to encrypt and decrypt a message, is that secure messages can be sent between two parties over an insecure communication channel without initially sharing secret information. The disadvantages are that encryption and decryption are slow, and the ciphertext can potentially be cracked by a cryptographer given enough time and computing power.
Asymmetric key cryptography, or public key cryptography, has revolutionized cryptography. Published in 1976, Martin Hellman and Whitfield Diffie describe a two-key cryptographic system, where one key is used for encryption and a second, different but related key is used for decryption. This has since become a key part of securing Internet communication. Asymmetric key cryptography is the basis for tools such as the Pretty Good Privacy Program (PGP), the Secure Sockets Layer (SSL) protocol, and the Transport Layer Security (TLS) protocol.
The confidentiality of a message and the authenticity of the sender can be guaranteed using asymmetric key cryptography. Imagine that Alice wants to communicate confidential information to Bob. Bob published a public key that he made available to Alice through unsecured channels. Alice uses a cryptographic algorithm and Bob’s public key to transform her text message into ciphertext, ensuring the confidentiality of her message. Only Bob can decrypt her message using a complementary algorithm and his private key. Bob can then reply with a message encrypted with her private key, and Alice can be sure that the message is authentic if her public key can decrypt it.
The strength of asymmetric key cryptography is related to the length of the keys and the difficulty of the math connecting the two keys. Ron Rivest, Adi Shamir and Leonard Adleman developed the RSA algorithm in 1978 which is the most common algorithm in use today. Public and private keys share the modulus of the product of two distinct large prime numbers. To ensure secure message encryption, key lengths had to increase. This is in response to an increase in computing power by hackers who could crack weaker code using brute force calculations. The complexity of the algorithms makes asymmetric key cryptography very slow and better suited for smaller messages such as sharing session keys used in digital signatures.
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