How Digital Signatures Work


How Digital Signatures Work

This is the simplest version of how a Digital Signature works. A “Digital Signature” is slightly different than an “Electronic Signature”, which is a broader term simply referring to any indication of agreement and identity.

A “Digital Signature” often refers to a Public / Private Key encryption system, the most common of which is “PGP”, or “Pretty Good Privacy”, which is a bit of humorous understatement as it’s the basis of most military security and included in export regulations as a U.S. national security secret.

The way this works is each person has TWO keys, one private, kept secret, and one public, which you publish online, give away freely, paste on your website, and add to a type of “public address book” called a keyserver. Anyone who wishes to ensure that only you will open a message will need this.

The way a digital signature (public / private key encryption) works is:

- The public key can only unscramble what the corresponding private key has protected.

- The private key can only decrypt what the corresponding public key has encrypted.

So when Bob sends Jane a message, and both want to be sure it’s kept secret.

Bob then encrypts the message using his personal private key (which ensures he’s the only writer, since Jane will later retrieve Bob’s “Public Key” from the key-server), and then encrypts it again, for the 2nd time, using Jane’s public key (which requires her private key in order to read).

This ensures that Jane is the only reader, and Bob was the only writer.

Anyone who wanted to maliciously forge Bob’s message would need access to Bob’s private key. Once any message is encoded using Jane’s public key, only her private key could make the message (or digital file) decipherable.Encrypting it only once using Jane’s public key ensures she’s the only reader, but anyone could have written it.

As a practical matter, many people are concerned over legal enforceability. To date, there have been numerous legal cases in which documents signed digitally were used or referenced, and digital signatures have been legally binding since signed into law since President Clinton. However, laws vary by jurisdiction outside the U.S. though they are legally binding within the E.U.

Electronic Signatures technically is a more liberal term referring to anything that shows identity and intent. This could be a digital signature, but could also be a pasted image or graphic signature, or digital signature that is not encrypted via a 3rd-party authentication disinterested party such as <a target=”_new” rel=”nofollow” onclick=”javascript:pageTracker._trackPageview(‘/outgoing/article_exit_link’);” rel=”external nofollow” target=”_blank” href=”http://www.iSignature.com”>http://www.iSignature.com</a>, an electronic signature service provider.

To get a free trial of the iSignature electronic signature system, please visit us at iSignature.

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  1. #1 by guzen on May 8th, 2010

    do you know how to add your signature to youtube videos

  2. #2 by nacao on May 8th, 2010

    Great job. i just have one question, what is the email address of document control?

  3. #3 by Xeo on May 8th, 2010

    There are a couple ways to do this. If your boss has a PC with the capability for a touch screen or a screen that you can write on he can actually sign his name on a document and then email it to you without ever printing it out.

    The most common way though is just a regular digital signature. You can create a secure web page that will display a document and will then ask for the user's digital signature. The user then types their full name and when they submitt it it record the ip address and the exact time submitted so that if any questions arise…The signature can be tracked own to a certain computer at a certain time. I know this is secure because I've applied for student loans online this way. As a safety measure you may want to make it where your boss needs to enter a password that is easy for him to remember and no one else knows (ex. social security number.) before he can even sign the document.
    Hope this helps ;)

  4. #4 by J.C on May 8th, 2010

  5. #5 by dinesh k on May 8th, 2010

    You must register with an agency that issues digital signatures. They can be verified or not. You will need to prove who you are by having a bank officer, etc vouch for you to have it verified. The digital signature agency maintains a "public key" and issues you a "private key". When you send the mail the signature is coded with the "private key". When someone decodes it with the "public key" it proves that you sent it and it wasn't altered. To use the key for a purpose such as taxes it needs to be verified in the manner that they require.

  6. #6 by earthlink on May 8th, 2010

    HI, great video. I’m trying to create my digital, handwritten signature on the computer so that I can sign my name on Word or pdf documents. Is it possible to create a handwritten signature using a mouse and Photo Shop and then be able to just paste it into a document as needed? Thank you.

  7. #7 by psychic on May 9th, 2010

    @cjkillashot

    Does the “Print Screen” button on your computer not work? Not sure I understand the question.

  8. #8 by urbantool on May 9th, 2010

    I put the name of my company under organization and then I put the business unit under Organization Name. ie: Bureau Veritas / Power & Utilities

  9. #9 by rails on May 9th, 2010

    @50unitedstates

    Not sure, I scanned my signature on paper and then saved it as an image, then attached that image to my signature.

  10. #10 by ramar on May 9th, 2010

    In layman's word, digital signature involves signing (adding a mark) on the documents for authentication and non-repudiation purpose.

    Here's the explanation quoted from howstuffswork.com

    A digital signature is basically a way to ensure that an electronic document (e-mail, spreadsheet, text file, etc.) is authentic. Authentic means that you know who created the document and you know that it has not been altered in any way since that person created it.
    Digital signatures rely on certain types of encryption to ensure authentication. Encryption is the process of taking all the data that one computer is sending to another and encoding it into a form that only the other computer will be able to decode. Authentication is the process of verifying that information is coming from a trusted source. These two processes work hand in hand for digital signatures.

  11. #11 by truth on May 9th, 2010

    how do i take pictures off of adobe acrobat that someone gave you

  12. #12 by Billa on May 10th, 2010

    ok – first start with 2 very large prime numbers
    one of these is kept secret and is called the private key
    the other is made public and is called the public key

    if i want to send you an email and i want to digitally sign it to prove it came from me i need to add some numbers (doesn't matter what numbers) to the end which i encrypt with my private key

    you receive the email and decrypt the extra numbers with my public key

    if you get the right numbers at the end then the email came from me – if not then someone has tampered with it

  13. #13 by sunil S on May 10th, 2010

    http://www.youdzone.com/signature.html

  14. #14 by corpo on May 10th, 2010

    What do you put on organization unit and organization name?

  15. #15 by Missy on May 11th, 2010

    Try these links:
    http://www.outbackphoto.com/workflow/wf_54/essay.html
    Go to Saving and Exporting Images to learn about embedding your information here: http://www.cellbio.duke.edu/faculty/klingensmith/Adobe%20Photoshop%207/Help/help.html

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