For this problem and the next few, consult Appendix P. In

Authors:

William Stallings

Chapter:

Electronic Mail Security

Exercise:

Problems

Question:5 | ISBN:9781292158587 | Edition: 7

Question

For this problem and the next few, consult Appendix P. In Figure P.2, each entry in the public-key ring contains an Owner Trust field that indicates the degree of trust associated with this public-key owner. Why is that not enough? That is, if this owner is trusted and this is supposed to be the owner’s public key, why is that trust not enough to permit PGP to use this public key?

Figure P.2:

S: 220 foo.com Simple Mail Transfer Service Ready
C: HELO bar.com
S: 250 OK
C: MAIL FROM:<Smith@bar.com>
S: 250 OK
C: RCPT TO:<Jones@foo.com>
S: 250 OK
C: RCPT TO:<Green@foo.com>
S: 550 No such user here
C: RCPT TO:<Brown@foo.com>
S: 250 OK
C: DATA
S: 354 Start mail input; end with <crlf>.<crlf>
C: Blah blah blah . . .
C: . . . etc. etc. etc.
C: <crlf><crlf>
S: 250 OK
C: QUIT
S: 221 foo.com Service closing transmission channel