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Securing E-Mail

Securing E-Mail. Xiaotao Jing. Outline. Security features of E-mail Confidentiality Sender authentication and Message integrity PGP(Pretty Good Privacy). S ecurity features of E-mail. Confidentiality Sender authentication Message integrity. . . K S ( ). K S ( ). +. +. +. -.

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Securing E-Mail

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  1. Securing E-Mail Xiaotao Jing

  2. Outline • Security features of E-mail • Confidentiality • Sender authentication and Message integrity • PGP(Pretty Good Privacy)

  3. Security features of E-mail • Confidentiality • Sender authentication • Message integrity

  4. . . KS( ) KS( ) + + + - KB(KS ) KB(KS ) KB KB + - KS KS(m ) KS(m ) m m KS Internet KS . . + - KB( ) KB( ) Confidentiality • Alice wants to send confidential e-mail m, to Bob. • Alice: • generates random symmetric private key, KS. • encrypts message with KS (for efficiency) • also encrypts KS with Bob’s public key. • sends both KS(m) and KB(KS) to Bob.

  5. . . KS( ) KS( ) + + + - KB(KS ) KB(KS ) KB KB + - KS KS(m ) KS(m ) m m KS Internet KS . . + - KB( ) KB( ) Confidentiality • Alice wants to send confidential e-mail m, to Bob. • Bob: • uses his private key to decrypt and recover KS • uses KS to decrypt KS(m) to recover m

  6. + - KA KA + - . . + - KA( ) KA( ) . . - - KA(H(m)) KA(H(m)) H(m ) m H( ) H( ) compare Internet m H(m ) m Sender authentication and Message integrity • Alice wants to provide sender authentication and message integrity. • Alice digitally signs message. • sends both message (in the clear) and digital signature.

  7. . KS( ) + + - KB(KS ) KA KB + + KS m . - KA( ) . - KA(H(m)) H( ) m Internet KS . + KB( ) Confidentiality , Sender authentication and Message integrity • Alice wants to provide secrecy, sender authentication, message integrity. Alice uses three keys: her private key, Bob’s public key, newly created symmetric key.

  8. PGP(Pretty Good Privacy) • An E-mail encryption scheme, de facto standard. • The creator, Phil Zimmerman, was target of a 3-year federal investigation. • Uses symmetric key cryptography, public key cryptography, hash function, and digital signature as described. • Provides confidentiality, sender authentication and message integrity.

  9. references • KUROSE, JAMES.F, and KEITH ROSS. “COMUPUTER NETWORKING : A Top-down Approach”. six edition.

  10. Thank you

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