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How to Generate your PGP Key pairs?

Post, Code and Quiet Time.

How to Generate your PGP Key pairs?

By Errong Leng – 22 Apr 2023 – View online →

Photo by Christoph Nolte / Unsplash

Strong recommend PGP Tool - Online PGP Key Generator Encryption Decryption Tool.

Notes: All the required options are import to generate the key pairs. Especially the name, email address and passphrase are critical for PGP decryption. "Name <Email address>" will be the user id of the generated PGP private key. You will use it with passphrase to decrypt the encrypted message by PGP public key.

I will write another 2 posts to guide how you can encrypt message using PGP public key and decrypt the data via PGP private key in Java. Stay tuned!

PGP

Pretty Good Privacy (PGP) is a data encryption and decryption computer program that provides cryptographic privacy and authentication for data communication. PGP is often used for signing, encrypting, and decrypting texts, e-mails, files, directories, and whole disk partitions and to increase the security of e-mail communications. It was created by Phil Zimmermann in 1991. PGP and similar software follow the OpenPGP standard (RFC 4880) for encrypting and decrypting data. Source: Wikipedia

PGP Tool - Online PGP Key Generator Encryption Decryption Tool

A simple and secure online client-side PGP Key Generator, Encryption and Decryption tool. Generate your PGP Key pairs, encrypt or decrypt messages easily with a few clicks.

Online PGP Key Generator Encryption Decryption Tool•Heiswayi Nrird, Bjar

GPG

GPG, or GNU Privacy Guard, is an open-source implementation of PGP encryption. It is functionally similar to PGP, but is available for free and can be used on a wider range of devices.

GPG, or "GNU Privacy Guard", is a newer encryption software that was released in 1997. It works in a similar way to PGP, but offers more features and is more widely-used. It's also free and open source, which means that its code can be examined and modified by anyone.

How to create GPG keypairs

Creating GPG keypairs in Linux is a simple process, but understanding how it works can enhance your security.

Enable Sysadmin•slauber

PGP vs GPG

Difference between PGP and GPG

Difference between PGP and GPG - PGP and GPG are both very powerful tools for encrypting your data. Some differences are there between the two which you should be aware of before making a decision about which one to use. Read this article to find out more about PGP and GPG and how they are different…

Technical Questions and Answers•Md. Sajid

How to get OAuth 2.0 access token with a certificate on the Microsoft identity platform?

Post, Code and Quiet Time.

How to get OAuth 2.0 access token with a certificate on the Microsoft identity platform?

By Errong Leng – 18 Apr 2023 – View online →

Photo by Adam Przeniewski / Unsplash

if you are familiar with OAuth 2.0, you should know how to make the request to the token endpoint with client id, client secret, scope and grant type.

Azure Active Directory (Azure AD) supports two types of authentication for service principals: password-based authentication (app secret) and certificate-based authentication. While app secrets can easily be created in the Azure portal or using a Microsoft API like Microsoft Graph, they're long-lived, and not as secure as certificates. It's therefore recommended that your application uses a certificate rather than a secret.

to be more secure, you might want to try with certificate-based authentication. According to this Microsoft Learn guide, the key part is to compute a client assertion from your ceritficate file. In another Microsoft Learn link, MSAL.NET has four methods to provide either credentials or assertions to the confidential client app. But how can you do the same compute in your Spring Boot java backend application as a OAuth 2.0 client?

use Spring Boot Starter for Azure Active Directory?

yup, Spring Boot Starter for Azure AD is a good fit for your java backend application if your app uses servelet. but you can't able to use if you used Reactive Spring WebFlux framework. Since spring-cloud-azure-starter-active-directory not support Reactive yet.

Spring Boot Starter for Azure Active Directory developer’s guide

This guide describes the features, issues, workarounds, and diagnostic steps to be aware of when you use the Azure Active Directory starter.

Microsoft Learn•KarlErickson

AadJwtEncoder.java

it is easy to make the request that post application/x-www-form-urlencoded body with required query to the access token endpoint according to OAuth 2.0 spec. You can do it in declarative way using a WebClient.

	import io.netty.handler.codec.http.HttpHeaderNames;
	import io.netty.handler.codec.http.HttpHeaderValues;
	import lombok.AllArgsConstructor;
	import org.springframework.http.MediaType;
	import org.springframework.http.ReactiveHttpInputMessage;
	import org.springframework.security.oauth2.core.endpoint.OAuth2AccessTokenResponse;
	import org.springframework.security.oauth2.core.web.reactive.function.OAuth2BodyExtractors;
	import org.springframework.stereotype.Component;
	import org.springframework.web.reactive.function.BodyExtractor;
	import org.springframework.web.reactive.function.BodyInserters;
	import org.springframework.web.reactive.function.client.WebClient;
	import reactor.core.publisher.Mono;

	@Component
	@AllArgsConstructor
	public class MSLAProviderImpl implements MSLAProvider {

	private final WebClient mslaWebClient;

	private final BodyExtractor<Mono<OAuth2AccessTokenResponse>, ReactiveHttpInputMessage> bodyExtractor = OAuth2BodyExtractors
	.oauth2AccessTokenResponse();

	@Override
	public Mono<OAuth2AccessTokenResponse> requestAccessTokenWithCertificate(String tenant, String scope, String clientId, String clientAssertion) {
	return mslaWebClient.post()
	.header(HttpHeaderNames.CONTENT_TYPE.toString(), HttpHeaderValues.APPLICATION_X_WWW_FORM_URLENCODED.toString())
	.body(BodyInserters
	.fromFormData("scope", scope)
	.with("client_id", clientId)
	.with("client_assertion_type","urn:ietf:params:oauth:client-assertion-type:jwt-bearer")
	.with("client_assertion", clientAssertion)
	.with("grant_type", "client_credentials")
	)
	.accept(MediaType.APPLICATION_JSON)
	.exchange()
	.flatMap((response) -> response.body(bodyExtractor));
	}
	}

view raw MSLAProviderImpl.java hosted with ❤ by GitHub

As you see, there is An assertion (a JSON web token) that you need to create and sign with the certificate you registered as credentials for your application. Though we can't use spring-cloud-azure-starter-active-directory in our Reactive Spring Boot app. but we still be able to use or refer to this AadJwtEncode::encode implementation and see how we can compute the client_assertion with the private key from your certificate.

How spring-cloud-azure-starter-active-directory compute client_assertion?

An assertion (a JSON web token) that you need to create and sign with the certificate you registered as credentials for your application. Read about certificate credentials to learn how to register your certificate and the format of the assertion.

azure-sdk-for-java/AadJwtClientAuthenticationParametersConverter.java at main · Azure/azure-sdk-for-java

This repository is for active development of the Azure SDK for Java. For consumers of the SDK we recommend visiting our public developer docs at https://docs.microsoft.com/java/azure/ or our versio...

GitHub•Azure

References

OAuth 2.0 client credentials flow on the Microsoft identity platform - Microsoft Entra

Build web applications by using the Microsoft identity platform implementation of the OAuth 2.0 authentication protocol.

Microsoft Learn•OwenRichards1

Microsoft identity platform certificate credentials - Microsoft Entra

This article discusses the registration and use of certificate credentials for application authentication.

Microsoft Learn•OwenRichards1

Create a self-signed public certificate to authenticate your application - Microsoft Entra

Create a self-signed public certificate to authenticate your application.

Microsoft Learn•henrymbuguakiarie

How to combine|merge multiple PDF files into a single file via itext pdf java lib?

Post, Code and Quiet Time.

How to combine|merge multiple PDF files into a single file via itext pdf java lib?

By Errong Leng – 18 Apr 2023 – View online →

Photo by Dessy Dimcheva / Unsplash

Here you go, the gist code sample using itext 5.

	import java.io.ByteArrayOutputStream;
	import java.io.IOException;
	import com.itextpdf.text.Document;
	import com.itextpdf.text.DocumentException;
	import com.itextpdf.text.pdf.PdfContentByte;
	import com.itextpdf.text.pdf.PdfImportedPage;
	import com.itextpdf.text.pdf.PdfReader;
	import com.itextpdf.text.pdf.PdfWriter;
	import reactor.core.publisher.Flux;
	import reactor.core.publisher.Mono;

	public class CombinePDF {

	private CombinePDF() {
	}

	public static Mono<byte[]> combinePDFs(Flux<byte[]> pdfs) {
	return pdfs.reduce(new ByteArrayOutputStream(), (out, pdf) -> {
	try {
	Document document = new Document();
	PdfWriter writer = PdfWriter.getInstance(document, out);
	PdfContentByte pageContentByte = writer.getDirectContent();
	document.open();
	PdfReader pdfReader = new PdfReader(pdf);
	for (int pageNumber = 1; pageNumber <= pdfReader.getNumberOfPages(); pageNumber++) {
	document.newPage();
	PdfImportedPage pdfImportedPage = writer.getImportedPage(
	pdfReader, pageNumber);
	pageContentByte.addTemplate(pdfImportedPage, 0, 0);
	}
	document.close();
	} catch (DocumentException \| IOException e) {
	e.printStackTrace();
	}
	return out;
	}).map(ByteArrayOutputStream::toByteArray);
	}
	}