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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

Securing E-Mail

Xiaotao Jing


Outline
Outline

  • Security features of E-mail

  • Confidentiality

  • Sender authentication and Message integrity

  • PGP(Pretty Good Privacy)


S ecurity features of e mail
Security features of E-mail

  • Confidentiality

  • Sender authentication

  • Message integrity


Confidentiality

.

.

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.


Confidentiality1

.

.

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


Sender authentication and message integrity

+

-

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.


Confidentiality sender authentication and message integrity

.

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.


Pgp pretty good privacy
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.


References
references

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



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