https://www.mkammerer.de/tags/crypto/Recent content in crypto on Moritz Halbritter's personal blogHugo -- gohugo.ioen-USTue, 25 Aug 2020 12:57:04 +0200https://www.mkammerer.de/blog/rsa-on-the-jvm/Tue, 25 Aug 2020 12:57:04 +0200https://www.mkammerer.de/blog/rsa-on-the-jvm/This post shows how to work with RSA on the JVM with the Java language. We’re gonna: Generate two keypairs (one for alice, one for bob) Save these keypairs to a file and load them again Send a message from alice to bob using a hybrid encryption scheme with confidentiality and authenticity Disclaimer: This post is intended to show the concepts underpinning a hybrid encryption scheme. This is not production ready code!https://www.mkammerer.de/blog/aes-ctr-encryption-with-java/Wed, 22 Apr 2020 17:27:58 +0200https://www.mkammerer.de/blog/aes-ctr-encryption-with-java/And another post about my pet peeve “crypto stuff”. This time I want to encrypt something with the AES cipher in CTR mode. The advantages of CTR are, quote wikipedia: CTR mode … also allows a random access property during decryption. CTR mode is well suited to operate on a multi-processor machine where blocks can be encrypted in parallel But keep in mind that CTR isn’t an AEAD mode, meaning you have to secure the ciphertext with additional tamper proofing, e.https://www.mkammerer.de/blog/encrypt-something-with-aes-how-hard-can-it-be/Mon, 07 Nov 2016 17:34:19 -0800https://www.mkammerer.de/blog/encrypt-something-with-aes-how-hard-can-it-be/As it turns out - it’s hard. Cryptography is hard to get right, and the thing is: you probably won’t know if you got it wrong. In this blog post I want to show a way to encrypt something in a secure way on the JVM, the language of my choice is Kotlin. AES has multiple modes: ECB, CBC, GCM and more. The easy way: GCM I’ll start with the simplest way to encrypt something with AES, using the GCM mode.https://www.mkammerer.de/blog/curve25519-and-aes-gcm-on-the-jvm/Tue, 29 Dec 2015 16:45:03 +0100https://www.mkammerer.de/blog/curve25519-and-aes-gcm-on-the-jvm/I wrote a small project in Kotlin to demonstrate the use of ECC with Curve25519 on the JVM. After agreeing on a shared secret, it uses SHA-256 to derive a session key and encrypts the payload with AES-GCM. If you’re interested in crypto, this may be something for you. See this repository for the code.https://www.mkammerer.de/blog/a-keyczar-tutorial/Fri, 06 Nov 2015 21:23:50 +0100https://www.mkammerer.de/blog/a-keyczar-tutorial/In this post I’ll show you how to use Keyczar and Java to exchange messages between two parties in a secure way. Keyczar is a great library, but it lacks some documentation. In this tutorial we use a SignedSession, that means: the sender and the receiver each has a key pair consisting of private and public “crypt” keys and a key pair of private and public “sign” keys. The crypt keys are used to encrypt/decrypt the message, the sign keys are used to sign/verify the message.https://www.mkammerer.de/blog/using-google-keyczar-with-gradle/Thu, 04 Jun 2015 20:11:18 +0200https://www.mkammerer.de/blog/using-google-keyczar-with-gradle/Google Keyczar is a framework for cryptography in Java and other languages. Unfortunately they don’t upload their artefacts to Maven Central and don’t provide documentation on how to add Keyczar to your Maven or Gradle project. To add Keyczar to Gradle, add the following in your build.gradle: repositories { // ... maven { url 'https://raw.githubusercontent.com/google/keyczar/master/java/maven/' } } dependencies { compile 'org.keyczar:keyczar:0.66' } This adds the Keyczar Maven repository, which is hosted on GitHub and adds a dependency on Keyczar 0.https://www.mkammerer.de/blog/secure-password-storage/Sun, 05 Apr 2015 18:57:12 +0200https://www.mkammerer.de/blog/secure-password-storage/I’ve written a blog post about secure password storage on the QAware blog, check it out if you are interested!