Comments on: Digital Signature?!

Question: Digital Signature?!

JonnyRotten — Wed, 22 Mar 2006 11:00:39 -0800

Digital "Signature" in an excel spreadsheet, is it easy and possible? My company wants to reduce our paper waste and do digital copies of some of our internal forms. But we need an easy way to digitally sign the documents throughout the various stages of approval.

I have found hardware/software packages that you can have a input pad to actually sign on, and then it gets inserted into the document. But I would prefer something that they can just (for example) to go -insert - add digital signature and BAM! it adds it to the active cell.

I guess problem number one is, a google search for digital signature turns up about 1 million pages for digital certificates, which are not what I want at all.

It doesn't have to be terribly secure, I would prefer it was something that would be somewhat hard to use if you weren't at the computer. User friendly is the biggest concern. Bonus points if it works in all office programs besides excel.

By: subtle-t

subtle-t — Wed, 22 Mar 2006 11:16:19 -0800

What about turning the signature into a truetype font?

By: subtle-t

subtle-t — Wed, 22 Mar 2006 11:19:07 -0800

Addendum - as long as no one else has access to the font, it can only be used on computers where it's installed.

By: teece

teece — Wed, 22 Mar 2006 11:19:55 -0800

Have you seen this?

It's what your asking for (sort of). But it does not look like it would handle a document that has been signed many times, as it passed from hand to hand. It looks more like a single document, single signature (to verify authenticity) kind of thing.

By: JonnyRotten

JonnyRotten — Wed, 22 Mar 2006 11:46:36 -0800

but, if you turn it into a true type font, and pass it to someone else, won't it show as the default font if they do not have your font installed on their computer?

teece, its definatly not a digital certificate that I am looking for. From what I have read, thats more for like.. Saying your VB code and Macros are safe and secure.

By: Psychnic

Psychnic — Wed, 22 Mar 2006 12:14:54 -0800

I can imagine some trick with the file attributes. You can access them by opening the file properties, then click the summary tab. I'm sure someone has already progammed that. See, for instance, this.

By: subtle-t

subtle-t — Wed, 22 Mar 2006 12:17:08 -0800

Ok, since you mentioned internal forms, I guess I assumed everyone in the org would get access to the font. I guess the problem is that everyone with access can use it to "sign" things.

By: teece

teece — Wed, 22 Mar 2006 12:22:08 -0800

teece, its definatly not a digital certificate that I am looking for. From what I have read, thats more for like.. Saying your VB code and Macros are safe and secure.

That's not what a digital signature (which is created with a key, which can be obtained in a digital certificate) does. This is what you want, it's just that it works at workbook level, and I don't know if it would support multiple signings (and it does not seem to work on the Mac version of Excel, so I can't find out).

You want to sign a document digitally. For that, you need a key. The general issue of whether or not you trust a key belongs to someone is handled by a certificate authority, which is where the certificates come in. They are part of a network of trust.

Once you buy a certificate, or make your own, you can sign an Excel workbook with this key. Once that is done, you will know that the given person ('s key) did the signing (and only that key), and that that file has not been modified since it was signed.

This is useful to know if a file has been tampered with by a virus, but it is by no means its only use.

By: teece

teece — Wed, 22 Mar 2006 12:26:34 -0800

Or are you not using the term "digital signature" in the way I am?

A digital signature, to me, is what I just outlined above.

But are you looking for some way to easily insert scans of someone's handwritten signature into an Excel file?

If so, sorry, but don't use the term digital signature there, as it will lead you astray. Digital signature has developed a cryptographic meaning with respect to computers (but it's not called that by accident -- it serves the same purpose [and more, and better] that a handwritten signature does in meatspace).

By: misanthropicsarah

misanthropicsarah — Wed, 22 Mar 2006 12:35:04 -0800

This may be too obvious, but what about saving everyone's signature as a jpg and then inserting that image where they need to sign? That's what I do. About as low-tech as you can get.

Have everyone sign a white piece of paper and scan it. Crop it, then save it at ~300dpi, at whatever width you want.

Or, if you have one of those fancy drawing things that input directly into an editing program, have them sign that.

But, like I said, I did it the low tech way, and it works fine for our office needs.

By: misanthropicsarah

misanthropicsarah — Wed, 22 Mar 2006 12:36:40 -0800

PS--I call it an e-signature....

By: Sharcho

Sharcho — Wed, 22 Mar 2006 12:42:31 -0800

I think what you probably want is a revision control system such as Subversion. That would work with any file type. Every user log ins with their username and password to the revision control system, and then you can always see for every revision who modified the file, when it was modified, and you can go back to any older version of the file, so you can always know who to blame. TortoiseSVN, the Subversion client for Windows, is very easy to use (so they say, I haven't actually used it).

By: Rock Steady

Rock Steady — Wed, 22 Mar 2006 13:54:15 -0800

OK, here's a low-tech, easy-use idea that may or may not work (as I know little about how fonts work). Create a font called "Signature" or something. Install on all machines. Add each signer's signature to the font as a single key, but make it a really random key combo (shift-alt-left bracket, for example). Assign each signer a different random key combo, and tell them not to reveal their unique combo. Someone could find others' signatures by trial and error, but you said it doesn't have to be terribly secure.