Usability of WKD

Criteria for implementing WKD with a good usability

In a bachelor thesis two use cases were developed which describe how users who don't have much experience with encryption can encrypt emails or check signatures with little effort and a good usability.
These use cases are used to name criteria which help developers to improve the usability of their products. They are also useful when it comes to a comparison between the usability of different products.
WKD-keys have a basic trust because they are fetched from WKD-servers that belong to email-providers. Reasons for that are that email-provider know that a pubkey belongs to an email-address and that email-providers usually have a higher security level than private persons who maintain a server. Some criteria reflect this basic trust of WKD-keys.

• C1 - Direct method: The product supports the direct method of WKD
• C2 - Advanced method: The product supports the advanced method of WKD
• C3 - WKD-ready: The product is ready for WKD without any preparations after a clean installation
• C4 - Offered in compose area: WKD is offered in the area where users enter an email-address. To fulfill this criterion it's sufficient that there is a button to start a key lookup. It's not necessary that WKD will be executed automatically. But, users shouldn't have to open additional windows before they can start the lookup.
• C5 - Offered in signature area: WKD is offered in the area where users check the signature of an email. Like for C4 users shouldn't have to open additional windows.
• C6 - Automatic WKD (Compose): The product uses WKD automatically when users enter an email-address in the area where they can compose an email. The users do not have to press a button to retrieve a key via WKD.
• C7 - Prefer WKD-keys (Compose): When the product has access to keys which were directly imported and don't contain any information about their trust and a WKD-key it should automatically use the WKD-key. This criterion applies to the area to compose an email.
• C8 - Prefer WKD-keys (Signature): When the product has access to keys which were directly imported and don't contain any information about their trust and a WKD-key it should automatically use the WKD-key. This criterion applies to the area to check the signature of an email.
• C9 - Displays basic trust (Compose): The product distinguishes between keys without any information about their trust and WKD-keys that have at least a basic trust. It displays this trust in the area to compose an email.
• C10 - Displays basic trust (Signature): The product distinguishes between keys without any information about their trust and WKD-keys that have at least a basic trust. It displays this trust in the area to check the signature of an email.

Usability of different products

Balsa

Criterion	Fullfilled	Tested version
C1: Direct method	yes	2.6.3
C2: Advanced method	yes	2.6.3
C3: WKD-ready	no	2.6.3
C4: Offered in compose area	no	2.6.3
C5: Offered in signature area	no	2.6.3
C6: Automatic WKD (Compose)	no	2.6.3
C7: Prefer WKD-keys (Compose)
C8: Prefer WKD-keys (Signature)
C9: Displays basic trust (Compose)
C10: Displays basic trust (Signature)

Claws Mail

Criterion	Fullfilled	Tested version
C1: Direct method	yes	3.18.0/4.0.0
C2: Advanced method	yes	3.18.0/4.0.0
C3: WKD-ready	no	3.18.0/4.0.0
C4: Offered in compose area	no	3.18.0/4.0.0
C5: Offered in signature area	yes	3.18.0/4.0.0
C6: Automatic WKD (Compose)	no	3.18.0/4.0.0
C7: Prefer WKD-keys (Compose)	no	3.18.0/4.0.0
C8: Prefer WKD-keys (Signature)	no	3.18.0/4.0.0
C9: Displays basic trust for WKD-keys(Compose)	no	3.18.0/4.0.0
C10: Displays basic trust for WKD-keys (Signature)	no	3.18.0/4.0.0

Evolution

Criterion	Fullfilled	Tested version
C1: Direct method	yes	3.48.1
C2: Advanced method	yes	3.48.1
C3: WKD-ready	yes	3.48.1
C4: Offered in compose area	yes	3.48.1
C5: Offered in signature area
C6: Automatic WKD (Compose)	yes	3.48.1
C7: Prefer WKD-keys (Compose)
C8: Prefer WKD-keys (Signature)
C9: Displays basic trust for WKD-keys(Compose)	no	3.48.1	Quiet the opposite because it is showing "Detailed error: Failed to encrypt: The key for recipient <email-address> is not trusted."
C10: Displays basic trust for WKD-keys (Signature)

FairEmail

Criterion	Fullfilled	Tested version
C1: Direct method	yes	1.1776
C2: Advanced method	yes	1.1776
C3: WKD-ready	no	1.1776
C4: Offered in compose area	no	1.1776
C5: Offered in signature area	no	1.1776
C6: Automatic WKD (Compose)	no	1.1776
C7: Prefer WKD-keys (Compose)	no	1.1776
C8: Prefer WKD-keys (Signature)	no	1.1776
C9: Displays basic trust for WKD-keys(Compose)	no	1.1776
C10: Displays basic trust for WKD-keys (Signature)	no	1.1776

K9Mail

Criterion	Fullfilled	Tested version
C1: Direct method	yes	5.806
C2: Advanced method	yes	5.806
C3: WKD-ready	no	5.806
C4: Offered in compose area	no	5.806
C5: Offered in signature area	no	5.806
C6: Automatic WKD (Compose)	no	5.806
C7: Prefer WKD-keys (Compose)	yes	5.806
C8: Prefer WKD-keys (Signature)	no	5.806
C9: Displays basic trust for WKD-keys(Compose)	no	5.806
C10: Displays basic trust for WKD-keys (Signature)	no	5.806

KMail

Criterion	Fullfilled	Tested version	Comment
C1: Direct method	yes	5.20.3
C2: Advanced method	yes	5.20.3
C3: WKD-ready	no	5.23.0	Have to enable Settings -> Configure KMail... -> Security -> Encrypt all messages when possible
C4: Offered in compose area	yes	5.20.3
C5: Offered in signature area	no	5.20.3
C6: Automatic WKD (Compose)	yes	5.20.3
C7: Prefer WKD-keys (Compose)	no	5.18.3
C8: Prefer WKD-keys (Signature)	no	5.18.3
C9: Displays basic trust (Compose)	no	5.23.0
C10: Displays basic trust (Signature)	no	5.20.3

Mailvelope

Criterion	Fullfilled	Tested version
C1: Direct method	yes	4.4.1
C2: Advanced method	yes	4.5.0
C3: WKD-ready	yes	4.4.1
C4: Offered in compose area	yes	4.4.1
C5: Offered in signature area	no	4.4.1
C6: Automatic WKD (Compose)	yes	4.4.1
C7: Prefer WKD-keys (Compose)	no	4.4.1
C8: Prefer WKD-keys (Signature)
C9: Displays basic trust (Compose)	no	4.4.1
C10: Displays basic trust (Signature)

GpgOL (Outlook)

Criterion	Fullfilled	Tested version	Comment
C1: Direct method	yes	2.5.3
C2: Advanced method	yes	2.5.3
C3: WKD-ready	yes	2.5.3
C4: Offered in compose area	yes	2.5.3
C5: Offered in signature area	yes	2.5.3
C6: Automatic WKD (Compose)	yes	2.5.3
C7: Prefer WKD-keys (Compose)	no	2.5.3	When sending an email GpgOL shows a dialog where the user has to select a key. The WKD key was pre-selected but it's not sure why.
C8: Prefer WKD-keys (Signature)	no	2.5.3
C9: Displays basic trust (Compose)	no	2.5.3
C10: Displays basic trust (Signature)	yes	2.5.3

Thunderbird

Criterion	Fullfilled	Tested version
C1: Direct method	yes	97.0a1
C2: Advanced method	yes	97.0a1
C3: WKD-ready	no	97.0a1
C4: Offered in compose area	no	97.0a1
C5: Offered in signature area	no	97.0a1
C6: Automatic WKD (Compose)	no	97.0a1
C7: Prefer WKD-keys (Compose)	no	97.0a1
C8: Prefer WKD-keys (Signature)	no	97.0a1
C9: Displays basic trust (Compose)	no	97.0a1
C10: Displays basic trust (Signature)	no	97.0a1