As I explained to you extensively in my tutorial on how to apply a digital signature, the digital signature (or digital electronic signature) is a tool that allows you to give legal validity to a document as if it had been signed in an autograph by a person. It is based on three principles: authenticity, as it allows to verify the identity of the signatory; integrity, as it ensures the originality and non-modification of signed documents and non-repudiation, as the signer of a document cannot repudiate the authorship of the latter.
To obtain the digital signature it is necessary to purchase a special certificate and a special kit from a certification body, but we have already talked about this extensively in the tutorial that I have just pointed out to you. Today I want to focus on another aspect: the verification of the digital signature. If we don't sign an electronic document, but we receive one, how do we make sure it's authentic? How do we understand if the signature inside it is valid and is therefore legally recognized? I'll explain it to you right away.
If you want to learn how to verify digital signature, all you have to do is download a special software on your computer or connect to an online digital signature verification service and give them the file you want to verify the authenticity (which can be in PDF or p7m format at depending on whether the signature is PAdES or CAdES). Within seconds you will get the test response with all the details relating to the signature included in the file: all for free and without the need to purchase special kits (those are only for digitally signing it, not for verifying it).
▶ ︎ Programs to verify digital signature | Verify digital signature online | Other solutions to verify digital signature
Programs to Verify Digital Signature
If you are ready to start and want to find out how to verify digital signature, take five minutes of free time and try one of the programs I am about to recommend. They are almost all free and multi-platform, meaning they work not only on Windows, but also on macOS and Linux. Furthermore, if you have a digital signature kit you may not even have to download them as they are already included in the kit you purchased.
The file formats that can be submitted for signature verification are: PDF (who can use the type signature Pads and keep their original format) e p7m (i.e. cryptographic envelopes that use signature CAdES and can contain any type of document). For more information, read on.
Dike is the software that comes with the InfoCert digital signature kits. It allows you to digitally sign electronic documents and verify documents already signed. The purchase of any kit or the use of smart cards or keys is not required to verify the signature. Another important thing to underline is that the program is completely free and works on all major PC operating systems: Windows, macOS and Linux.
To download Dike on your PC, connect to the InfoCert site using the link I just provided, scroll the page to the bottom and click on the logo of the operating system you have installed on your PC, for example the windows flag or macOS apple. Once the download is complete, if you use a PC Windows, open the file DIke6-installer-win32.msi and click on the button forward. Then accept the conditions of use of the software, putting the check mark next to the item I accept the terms of the license agreement, and finish the setup by clicking on forward, forward, Install, Yes e end.
If you use a Poppy, to install Dike all you have to do is open the dmg package that contains the latter and drag the program icon into the folder Applications say macOS.
At this point, to verify a digital signature with Dike, click on the button Verifica and select the PDF or p7m file of your interest to view the application response. Alternatively, if you prefer, you can take the file to be checked and drag it directly onto the button Verifica by Dike.
If the signature of the document you have selected is valid, you will see the message appear The signature was successfully verified and by clicking on the button Details located at the top right, you will be able to view all the details relating to the latter. If the signature is not valid, you will see the message Invalid signature and by clicking on the button Report, you will be able to view all the details of the error.
Please note: if you are told that updates are available for the certificate list, agree to install them.
ArubaSign (Windows / Mac / Linux)
As easily understood, Aruba Sign is the software that allows you to affix, manage and verify the digital signatures included in the Aruba digital signature kits. It is completely free and is compatible with Windows, macOS and Linux. To verify digital signatures, it can also be used without a smart card or signature kit.
To download Aruba Sign on your PC, connected to the Aruba website using the link I just provided, click on the item Software di firma ArubaSign e pulsing sul pulsating Download the software related to the operating system installed on your computer. Once the download is complete, if you use a PC Windows, open the file ArubaSign-xx.exe and complete the application setup by first clicking on Yes and then OK, again Yes, forward, Install e end.
If you use a Poppy, to install Aruba Sign all you have to do is open the dmg package which contains the latter and copy the program icon into the folder Applications say macOS.
When installation is complete, to verify your PDF or p7m files with Aruba Sign, start the program, wait for the certificate update to be performed and drag the document to be verified on the button Verifica (or presses on the latter and selects the document to be checked "manually").
Within a few seconds, a window will open with the details of the signature included in the file you have selected and you will be told if it is valid or not.
FirmaOK! (Windows / Mac / Linux)
Another software that allows you to verify the digital signature is FirmaOK !, which is included in the digital signature kits of Poste Italiane but can also be used in mode (as regards the verification of signatures, to sign documents obviously you have to buy a kit). It's free and compatible with all major PC operating systems: Windows, macOS and Linux.
To download FirmaOK! on your computer, connect to the Poste Italiane website using the link I just provided and click on the link Setup firmaOK! Windows 32bit e 64bit if you use Windows, on the link Setup firmaOK! MacOS if you use macOS or on the link Setup firmaOK! Linux 32bit e 64bit if you use Linux.
To download completed, a PC Windows, open the archive signatureOK_Win.zip, extract the contents to a folder of your choice and run the installation package named signatureOK_installer_xx.exe. In the window that opens, click the button forward, metti il segno di spunta accanto alla voce I accept the license conditions and complete the setup by clicking on first forward three consecutive times and then on Install e end.
If you use a Poppyinstead, open the file signatureOK_MacOS.zip and extract the contents to a folder of your choice. Then open the dmg package which contains FirmaOK !, click on the button Accept and drag the program icon to the folder Applications say macOS.
When installation is complete, start FirmaOK !, drag the document to validate on the button Verifica and wait for the window with the check result to appear. If you are asked to download an update for signing certificates, accept.
Adobe Reader/Adobe Acrobat (Windows/Mac)
If you have a recent version of Adobe Reader or Adobe Acrobat installed on your PC, you can check the signatures included in PDF files simply by opening them, calling the signature panel (the pen icon located in the left sidebar) and expanding the item related to signature present in the document.
If the warning appears on the screen "Trusted certificates are available for download, which improve the use of signed documents. Would you like to install them?", answer in the affirmative. This way Adobe Reader (or Acrobat) will download the latest certificates and will be able to validate digital signatures more effectively. The same procedure cannot be followed for files in p7m format.
Verify Digital Signature Online
Do you need to verify the digital signature on some very light files? Don't have your signature kit handy and / or don't feel like installing new programs on your PC? No problem. Here are some online services that allow you to verify the digital signature directly from the browser. They are all free and extremely simple to use.
Digital Signature Service
Digital Signature Service is a service sponsored by the European Commission which aims to facilitate the validation of electronic documents signed in the various Member States. To use it, all you have to do is connect to its home page and click on the item Validate a signature located in the left sidebar.
On the page that opens, click on the button Choose File / Browse placed next to the item Signed file, select the PDF / p7m file to be examined, press the button Submit and within a few seconds you will have the result of the test.
PosteCert di Poste Italiane also offers a convenient service for verifying the digital signature online. The service is completely free, requires no registration and works with all major web browsers. Its only limitation is that it only allows you to scan files no larger than 50MB.
To start the validation of a PDF or p7m file, all you have to do is connect to the PosteCert home page, press the button Choose File / Browse, select the file to check and press the button Verify company which appears below.
Within a few seconds, the page with the result of the analysis and all the details on the signature included in the document you selected will open.
If you do not want to download the InfoCert software, you can take advantage of the online verification tool offered by the latter and validate your documents directly from the browser. To use the validation service, all you have to do is connect to its main page, and select the tab Verify digital signature.
At this point, click on your button Choose File / Browse, select the PDF or p7m file to be examined and press the button I accept and verify to get the test result. If after clicking on the "I accept and verify" button you do not see the result of the check appear (it should be displayed at the bottom of the page), try using another browser, such as Chrome.
Other Solutions to Verify Digital Signature
If you want an even broader list of software and online services to verify digital signature, consult the website of the Agency for Digital Italy, which hosts a very large list of resources to verify signature certificates included in PDF files, p7m etc.