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As it turns out, Stephan lost the sheet of paper with his contact QR code. Tom Duffy picks it up and sends Stephan his contact information. Stephan makes the mistake of trusting him and adds him to his contacts. They converse in the manner shown above and eventually Stephan catches on and removes Tom Duffy (known to Stephan as Bob) from his contacts, erasing all evidence of communication.
Learnability: By the point where a user feels the need to erase evidence of communication, he or she should be familiar enough with the interface to have seen the Actions menu. However, he or she may not know that there exists an option to remove records of communication. This should not be a problem as he or she will see this feature as he or she attempts to delete the contact.
Efficiency: This action is inefficient and requires 4-5 clicks. In this case, this is a non-issue because this feature will only be used rarely.
Safety: The user cannot undo deleting a contact (for security reasons). The application tries to communicate this to the user to reduce the changes of an error. Additionally, the interface repeatedly mentions the name of the contact being removed.
Design 2
Adding/Managing Contacts
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Storyboard | Learnability
| Efficiency
| Safety
|
|---|
 Secure Chat Window
Stephen must now update the team with new orders. On the Messaging tab,
Stephen can see a conversation with an individual or group, much like the
standard chat application on his phone. In this case, his can message John Doe
securely because he has a public key stored for him. The application reminds him
that he can securely communicate via color (background color), and each past
message that was sent with encryption is also set off by color and a lock icon. Groups
can be handled similarly to individuals with a group key.
Touching on the message area to enter a message brings up the keyboard and a lock
button, giving access to encryption options for the message (encrypt via personal
private key or public key of John Doe). The default encrypts via public key to ensure
safety, but Stephen can remove this if he decides encryption is not necessary for a particular message.
. 
||||\Unsecure Chat Window
This is the same view of the messaging window but for a contact without a stored
public key. The background color is red, reminding Stephen that no message can
be sent securely, and the lock icon near the message window is disabled.
| Pros: Mimics Conversation/Chat flow concepts.
Multiple signals for secure or unsecure communications
(lock icon near name, Lock on each securely sent/received
message, background color, message bubble color).
Cons: User must learn difference between using public or
private key.
| Pros: Streamlined interface for all secure and
unsecure communications with a single person or
group.
Default option uses secure public key encryption,
which requires user intervention if a different option
is desired (assumes this is the most likely selected
option).
Cons: Receiving a secure message
requires decryption using either personal private
or contact's public key, requiring extra time.
| Pros: Multiple visual cues to signify message security.
Cons: User can still send an unsecure message, so there
is still risk of secret information being sent unsecurely.
|
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