斗 长 Public-key Encryption ￥斗 ★★ o Why include“ from zou” in the message? So that receivers know the message comes from zou so that s/hewill use zou-publickeyto decode thetext o This is called a digital signature Can detect any change to the data
26 Public-key Encryption Why include “from zou” in the message? – So that receivers know the message comes from zou – so that s/he will use zou-public key to decode the text This is called a “digital signature” – Can detect any change to the data
斗 长 Public-key Encryption ￥斗 ★★ o If using public-keyencryption for privacy, do crypt(message, receiver-public o Anyone can send this message(no authentication o Only receiver can read it
27 Public-key Encryption If using public-key encryption for privacy, do – crypt (message, receiver-public) Anyone can send this message (no authentication) Only receiver can read it
斗 长 Public-key Encryption ￥斗 ★★ o Using PK encryption for authentication and privacy, crypt ("from zou crypt(msg, zou-private), receiver-public) o Only receiver can read this o Only zou can send it
28 Public-key Encryption Using PK encryption for authentication and privacy, – crypt (“from zou” crypt (msg, zou-private), receiver-public) Only receiver can read this Only zou can send it
斗 长 Public-key Encryption ￥斗 ★★ o Does the following work? from zou"crypt(crypt(message, receiver-public), zou private)
29 Public-key Encryption Does the following work? – “from zou” crypt (crypt (message, receiver-public), zouprivate)
斗 长 Example Public-key System: RSA ￥斗 ★★ 9 1978 by ron Rivest, Adi shamir, Leonard Adleman o Principle Multiplication and module is easy While factoring is difficult!
30 Example Public-key System: RSA 1978 by Ron Rivest, Adi Shamir, Leonard Adleman Principle: – Multiplication and module is easy – While factoring is difficult!