Software engineer & consultant · Oslo, NO

Kristoffer
Opsahl

Backend full-stack, strongest on security. Mostly Java, Spring Boot & React with Apache Kafka for event-driven systems. Also Elixir & Phoenix, Rust, Go, and React Native (iOS, Android, Web).

Distributed Systems
Event-Driven Architecture
Application Security
Cryptography

BashDockerForgejo ActionsPasskeysOAuth 2.0GCPKubernetesWebAuthnTypeScriptElixirJavaJWTDebianKotlinReactMySQLRustExpoKeycloakReact NativePostgreSQLSQLSQL ServerReact Native WebGoCaddySpring BootPhoenixSAML 2.0OpenID ConnectLinuxAzureiOSApache KafkaGitLab CI/CDFIDO2GitHub ActionsAndroid

Latest

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2026-04-03

How to Securely Erase a Hard-Disk Drive

LinuxNote

2025-12-07

Coding Agents Need Deterministic Feedback: A Case for Phoenix

AIElixir

2025-09-14

Using dd to Write an .iso to a USB Drive

LinuxNote

2025-07-07

My Alacritty, Zellij, and Helix Development Setup

ToolingNote

2025-04-29

Breaking AES-ECB with an Encryption Oracle Attack

SecurityCryptography

2025-04-22

3rd Prize at TG:HACK

SecurityCTF

2025-03-25

Java's Optional Has a Problem

Java

2025-03-07

From Zero to Hello World with Apache Kafka® in 2025

KafkaTutorial

2025-03-06

Core Concepts in Apache Kafka®

Kafka