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Securing E-Mail

This outline discusses critical security features of email communication, focusing on confidentiality, sender authentication, and message integrity. It delves into practical encryption techniques using PGP (Pretty Good Privacy), illustrating how confidential emails can be securely sent between users. The example of Alice sending a confidential message to Bob highlights the generation of random symmetric keys, the use of public key encryption, and digital signatures to ensure that messages remain secret and untampered with. Understanding these concepts is essential for safe email practices.

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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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