文档介绍：第九章公钥密码学与RSA
Private-Key Cryptography
traditional private/secret/single key cryptography uses one key shared by both sender and receiver
if this key is munications promised
also is symmetric, parties are equal
hence does not protect sender from receiver forging a message & claiming is sent by sender
Public-Key Cryptography
probably most significant advance in the 3000 year history of cryptography
uses two keys – a public & a private key
asymmetric since parties are not equal
uses clever application of number theoretic concepts to plements rather than replaces private key crypto
Why Public-Key Cryptography?
developed to address two key issues:
key distribution – how to have munications in general without having to trust a KDC with your key
digital signatures – how to verify a es intact from the claimed sender
public invention due to Whitfield Diffie & Martin Hellman at Stanford Univ. in 1976
known earlier in munity
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
Public-Key Characteristics
Public-Key algorithms rely on two keys where:
it putationally infeasible to find decryption key knowing only algorithm & encryption key
it putationally easy to en/decrypt messages when the relevant (en/decrypt) key is known
either of the two related keys can be used for encryption, with the other used for decryption (for some algorithms)
Public-Key Cryptosystems
Public-Key Applications
can classify uses into 3 categories:
encryption/decryption (provide secrecy)
digital signatures (provide authentication)
key exchange (of session keys)
some algorithms are suitable for all uses, o