CAB240 Lecture Notes - Lecture 10: Public-Key Cryptography, Symmetric-Key Algorithm, Key Distribution
Document Summary
Symmetric cipher uses the same key to encrypt and decrypt, leaving the problem of safely and securely distributing keys amongst the users. This can be done a number of ways (covered in the previous lecture: distribute out-of-band, diffie-hellman agreement, trusted third party (ttp, these aren"t always appropriate or viable in some online situations (e. g. banking) There is also a browser trust model that details how your browser decides which pks to trust. Public keys can be distributed by key servers and value verified by fingerprints: each user, has a key ring containing public keys of other users they trust, may sign public keys that they trust, e. g. The ca is vouching for the information in the certificate: a digital certificate contains, the user"s pk, the user"s id, other information (e. g. validity period) Digital certificates and trust: most widely used format for digitate certs: x. 509 standard, recommended by international telecommunication union (itu-t)
