(a) Explain how the client would obtain the public key and validate the email server’s digital signatures. (b) Discuss the problem of trusting the obtained public key and how this solution results in public keys that can/cannot be trusted. (c) Indicate whether you believe this approach could be used to prevent forged emails and explain why it would/would not be possible to send counterfeit emails in such a system.
One of the problems with the Internet email system is that sending forged emails is relatively straightforward, i.e., it is easy to send an email with a fake sender/from address. One solution to this problem would be for a domain’s mail servers to digitally sign any email originating from the domain. For this to be useful, the public key would need to be made available to clients to validate the signatures. It is proposed that the public keys of the mail servers will be verified and signed by a certification authority (same as SSL/TLS certificates) and distributed via a standardised URL for the domain, e.g., https://mybusiness.com/email.pubkey.
(a) Explain how the client would obtain the public key and validate the email server’s digital signatures.
(b) Discuss the problem of trusting the obtained public key and how this solution results in public keys that can/cannot be trusted.
(c) Indicate whether you believe this approach could be used to prevent forged emails and explain why it would/would not be possible to send counterfeit emails in such a system.
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