Demonstration how to sign a PDF using certificate
I want to share how to sign a pdf from the very beggining when I haven't forgot everyting.
First thing first it is noce to know what is a pdf signature and how you can make it in other programms. Here go videos I like:
- What is a pdf signature?: https://www.youtube.com/watch?v=6XsDVx0tjLc&ab_channel=RichardOliverBray
- Example of the signing in other applications: https://www.youtube.com/watch?v=EKpnaQG-LJs&ab_channel=AsoftClick
Basically, to make a digital sign (not electronic sign) of a PDF you have to have two thing: a PDF to sign and a certificate. Also, you can create a certificate (I have done it too). Good article about it:
- How to digitally sign a PDF?: https://medium.com/caution-your-blast/how-to-digitally-sign-a-pdf-programmatically-using-javascript-nodejs-54194af7bdc3
We will use two libraries: spongycastle and pdfbox-android
The spongycastle (https://glossarytech.com/terms/android/spongycastle) is the bouncycastle with little work around so it is easier use on Android. But it is up to you which one to use. It will be used for cryptographic algorithms in order to make your application secure and also to generate a certificate.
THe pdfbox-android is the pdfbox by Apache with little work around so it is easier use on Android. There are many other libraries (like iText), but be careful not to mess up with the licence (using iText you have to make your code open source). It will be used for signing a PDF.
Lets start from creating a new certificate. I think we should do it first to understand what it is and how it is build. Good article about it:
- Self Sign Certificate Creation: https://medium.com/@bouhady/self-sign-certificate-creation-using-spongy-castle-for-android-app-61f1545dd63
- https://stackoverflow.com/questions/26311678/how-to-create-certificate-pfx-file-in-java
- Create signature: https://www.tutorialspoint.com/java_cryptography/java_cryptography_creating_signature.htm
- If using bouncycastle: https://www.programcreek.com/java-api-examples/?api=org.bouncycastle.x509.X509V3CertificateGenerator
As you can see, there are a lot of new things like KeyStore... It is a good book (if you want to dive in):
- Secure Key Storage and Secure Computation in Android: https://www.ru.nl/publish/pages/769526/scriptie_tim_cooijmans.pdf
Also, these classes might be usefull too:
- CreateSignature: https://pdfbox.apache.org/docs/2.0.2/javadocs/index.html?org/apache/pdfbox/examples/signature/CreateSignature.html
- KeyStore: https://docs.oracle.com/javase/7/docs/api/java/security/KeyStore.html
- Android Keystore Type which one should I choose?: https://stackoverflow.com/questions/5700708/android-keystore-type-which-one-should-i-choose
- https://www.tabnine.com/code/java/methods/java.security.KeyStore/load
Creating a singing. There are some very good articles:
- HOW TO DIGITALLY SIGN PDF FILES?: https://jvmfy.com/2018/11/17/how-to-digitally-sign-pdf-files/
- Get the eBook "Digital Signatures for PDF Documents": https://itextpdf.com/en/resources/books/digital-signatures-pdf
Future plans: There is an option to add a Time Stamp to your signing. It may help:
Other useful matherials:
- Create signature: https://www.tutorialspoint.com/java_cryptography/java_cryptography_creating_signature.htm
- GitHub issue about the signing: TomRoush/PdfBox-Android#108
- Code example signing implementation: https://svn.apache.org/repos/asf/pdfbox/trunk/examples/src/main/java/org/apache/pdfbox/examples/signature/CreateSignature.java (colour version: https://svn.apache.org/viewvc/pdfbox/trunk/examples/src/main/java/org/apache/pdfbox/examples/signature/CreateSignature.java?view=markup) Other:
- https://github.com/BrentDouglas/pdfbox/blob/master/examples/src/main/java/org/apache/pdfbox/examples/signature/CreateSignature.java
- https://github.com/BrentDouglas/pdfbox/blob/0d731505e616081e66e6bda69af563b96711c2eb/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/interactive/digitalsignature/SignatureInterface.java#L30
- https://jar-download.com/artifacts/org.apache.pdfbox/pdfbox-examples/2.0.1/source-code/org/apache/pdfbox/examples/signature/CreateVisibleSignature.java
- https://stackoverflow.com/questions/47550563/pdf-signing-with-bouncycastle-using-pdfbox-2-x-x
- https://github.com/mkl-public/testarea-pdfbox1/blob/master/src/main/java/mkl/testarea/pdfbox1/sign/CreateSignature.java
- https://svn.apache.org/viewvc/pdfbox/branches/2.0/examples/src/main/java/org/apache/pdfbox/examples/signature/
- https://gist.github.com/jeff-sleek/9dccc4dfcbe9416608daf0862f75e354
- https://www.tutorialspoint.com/java_cryptography/java_cryptography_creating_signature.htm
- https://www.baeldung.com/java-digital-signature
- https://ec.europa.eu/digital-building-blocks/DSS/webapp-demo/doc/dss-documentation.html
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent