digital signatures

Yve_Ke

New Member
Joined
Jan 6, 2011
Messages
26
Can someone explain to me digital signatures in laymen's terms? For example what is the difference between digital signature and digital certificate. And where does the "trusted publishers" come into it at the Trust Centre. And is this true you need to buy them from an external source? I have had a look on the internet for information but I am still confused.
 

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Jerry Sullivan

MrExcel MVP
Joined
Mar 18, 2010
Messages
8,787
Hi,

There is a pretty good explanation in Excel 2007's Help under the topic:
"Get or create your own digital signature"

I've created my own digital signature (for free) that I use to distribute templates and other workbooks with macros within our company. It allows users to do a one-time acceptance that I am a "Trusted Publisher", and therefore they don't have to enable macros each time they open an xlsm document from me.

Check out that Help Article and if you have any questions, just post them to this thread.
 

Yve_Ke

New Member
Joined
Jan 6, 2011
Messages
26
Hi,

There is a pretty good explanation in Excel 2007's Help under the topic:
"Get or create your own digital signature"

I've created my own digital signature (for free) that I use to distribute templates and other workbooks with macros within our company. It allows users to do a one-time acceptance that I am a "Trusted Publisher", and therefore they don't have to enable macros each time they open an xlsm document from me.

Check out that Help Article and if you have any questions, just post them to this thread.
I don't understand why you would create your own digital signature - isn't it the same as creating a read only copy of a workbook? Is there any diffference? Also it says it only works on the computer that you created the digital signature - so what then would be the point of it?

Also, when I open a workbook with a digital signature - it says that the " author has marked it final for editing but you can "edit it anyway?" And if you do, then it removes the signature.

Also what is the difference between adding a digitial signature via the "Prepare command" and using the Signature line in the "insert" command.

As you can see I am totally confused.
 

Jerry Sullivan

MrExcel MVP
Joined
Mar 18, 2010
Messages
8,787
Wow that's a lot of questions. :)
I'll try my best to explain what I know.

I don't understand why you would create your own digital signature - isn't it the same as creating a read only copy of a workbook? Is there any diffference?
No, the Digital Signature doesn't protect or lock the workbook in any way. It merely gives the receiver of the workbook some assurance that the macros were last edited by a trusted source.

Also it says it only works on the computer that you created the digital signature - so what then would be the point of it?
I have created a digital signature on my computer and that signature can only be applied to documents from my PC. However, I can send a document with that digital signature applied to 100 people in my company.

Each person can go through a few steps to "install" my certificate on their computer. If they trust me, then they can choose to always trust documents that have that digital signature from me applied.

Even though my signature is "installed" in their computers, they won't be able to apply my signature to another document (in a sense forging my signature). That is what is meant by the phrase you read "only works on the computer that you created the digital signature"

Also, when I open a workbook with a digital signature - it says that the " author has marked it final for editing but you can "edit it anyway?" And if you do, then it removes the signature.
The Digital Signature won't prevent someone from changing my macros, but if they make changes, my signature will be removed- making it clear that I no longer can assure the integrity of that workbook.

Also what is the difference between adding a digitial signature via the "Prepare command" and using the Signature line in the "insert" command.
I haven't used those tools to add digital signatures to VBA projects, I typical just add them in the VBA Editor using Tools > Digital Signature.

I've been assuming you were referring to applying Digital Signatures for VBA macros, but you can also use them as a way to sign documents (like letters or reports) electronically, so the receiver knows that it came from you. I think the two tools you mentioned are designed with that use in mind.

Hope this helps!
 

Yve_Ke

New Member
Joined
Jan 6, 2011
Messages
26
Thanks Jerry, that does clear it up for me. I guess I was placing more emphasis on these digital signatures as a security measure but they are actually more there in an advisory capacity. I guess you can protect your workbook with passwords etc but how to proctect a user from a macro is a bit more tricky, ie if you still want to be able to run the macro. Digital signatures are just a way to make a person feel secure about the macro workbook.

Thanks so much for your help. Sometimes you can read and read about this in the textbooks but it isn't till you are actually able to discuss with someone that it makes sense.
 

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