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Public Key Cryptography and the RSA Algorithm

traditional private/secret/single key cryptography uses one key Key is shared by both sender and receiver if the key is disclosed communications are compromised also known as symmetric, both parties are equal hence does not protect sender from receiver forging a message & claiming is sent by sender | Public Key Cryptography and the RSA Algorithm Cryptography and Network Security by William Stallings Lecture slides by Lawrie Brown Edited by Dick Steflik Private-Key Cryptography traditional private/secret/single key cryptography uses one key Key is shared by both sender and receiver if the key is disclosed communications are compromised also known as symmetric, both parties are equal hence does not protect sender from receiver forging a message & claiming is sent by sender So far all the cryptosystems discussed have been private/secret/single key (symmetric) systems. All classical, and modern block and stream ciphers are of this form. Public-Key Cryptography probably most significant advance in the 3000 year history of cryptography uses two keys – a public key and a private key asymmetric since parties are not equal uses clever application of number theory concepts to function complements rather than replaces private key cryptography Will now discuss the radically different public key systems, in which two keys are used. Anyone knowing the public key can encrypt messages or verify signatures, but cannot decrypt messages or create signatures, counter-intuitive though this may seem. It works by the clever use of number theory problems that are easy one way but hard the other. Note that public key schemes are neither more secure than private key (security depends on the key size for both), nor do they replace private key schemes (they are too slow to do so), rather they complement them. Public-Key Cryptography public-key/two-key/asymmetric cryptography involves the use of two keys: a public-key, which may be known by anybody, and can be used to encrypt messages, and verify signatures a private-key, known only to the recipient, used to decrypt messages, and sign (create) signatures is asymmetric because those who encrypt messages or verify signatures cannot decrypt messages or create signatures Public-Key Cryptography Stallings Fig 9-1. Why Public-Key Cryptography? | Public Key Cryptography and the RSA Algorithm Cryptography and Network Security by William Stallings Lecture slides by Lawrie Brown Edited by Dick Steflik Private-Key Cryptography traditional private/secret/single key cryptography uses one key Key is shared by both sender and receiver if the key is disclosed communications are compromised also known as symmetric, both parties are equal hence does not protect sender from receiver forging a message & claiming is sent by sender So far all the cryptosystems discussed have been private/secret/single key (symmetric) systems. All classical, and modern block and stream ciphers are of this form. Public-Key Cryptography probably most significant advance in the 3000 year history of cryptography uses two keys – a public key and a private key asymmetric since parties are not equal uses clever application of number theory concepts to function complements rather than replaces private key cryptography Will now discuss the radically different public