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Secure Email: Confidentiality, Authentication, and Message Integrity

Learn how to ensure secure email communication with confidentiality, sender authentication, and message integrity. Explore symmetric and public key encryption methods and the use of digital signatures.

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Secure Email: Confidentiality, Authentication, and Message Integrity

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  1. Chapter 8 roadmap 8.1 What is network security? 8.2 Principles of cryptography (confidentiality) 8.3 Message integrity 8.4 End-point authentication 8.5 Securing e-mail (application) 8.6 Securing TCP connections: SSL (transport) 8.7 Network layer security: IPsec (network) 8.8 Securing wireless LANs (MAC) 8.9Operational security: firewalls and IDS Network Security

  2. Secure e-mail • Alice wants to send secure e-mail, m, to Bob • confidentiality • sender authentication • message integrity • receiver authentication • Confidentiality • Symmetric key • key distribution issue • public key encryption • but not efficient for long messages • (symmetric, private) session key Network Security

  3. . KS( ) + + KB(KS ) KB + . + KB( ) Secure e-mail (confidentiality) • Alice wants to send confidential e-mail, m, to Bob. KS KS(m ) m Internet KS • Alice: • generates random symmetric private session 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 Network Security

  4. . . KS( ) KS( ) + + + - KB(KS ) KB(KS ) KB KB - + KS KS(m ) KS(m ) m m KS Internet KS . . + - KB( ) KB( ) Secure e-mail (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 Network Security

  5. + - KA KA - + . . + - KA( ) KA( ) . . - - KA(H(m)) KA(H(m)) H(m ) m H( ) H( ) compare Internet H(m ) m m Secure e-mail (auth. + msg integrity) Alice wants to provide sender authentication & message integrity (but no confidentiality) • Alice digitally signs message (digital signature) • sends both message (in the clear) and digital signature Network Security

  6. . KS( ) + - + KB(KS ) KB KA + + KS m . - KA( ) . - KA(H(m)) H( ) m Internet KS . + KB( ) Secure e-mail (all) • Alice wants to provide confidentiality, sender authentication, and message integrity. Alice uses three keys: her private key, Bob’s public key, newly created symmetric key Network Security

  7. . KS( ) + - + KB(KS ) KB KA + + KS m . - KA( ) . - KA(H(m)) H( ) m Internet KS . + KB( ) Secure e-mail (all) • Alice wants to provide confidentiality, sender authentication, and message integrity. Alice uses three keys: her private key, Bob’s public key, newly created symmetric key Network Security

  8. Secure e-mail (all) • Alice and Bob to obtain each other’s public keys! • certify public keys using CA (CA-signed certificates) • receiver authentication Network Security

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