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I'm Sean O'Neil, a senior software engineer and information-security expert based in Cairns, Australia. I bring 40+ years of hands-on experience across systems programming, optimisation, reverse engineering, and secure-software architecture. My deep expertise includes C, C++, C#, PowerShell, Intel x86/x64 assembly, compression algorithms, cryptography, and Windows internals. I specialise in reverse engineering closed-source software to recover undocumented file formats, encryption and compression schemes, and communication protocol details to enable interoperability across heterogeneous systems. I've authored cryptographic systems and high-performance algorithms such as PureNoise (IRC encryption, 2000), VEST ciphers (eSTREAM candidates), EnRUPT (NIST SHA-3 candidate). As a former Chief Information Security Officer, I excel at turning complex, slow codepaths into high-performance, low-latency, multi-threaded, vectorised solutions. I'm passionate about extreme software optimization—optimizing CPU cache behaviour, SIMD vectorization, memory layouts, and GPU acceleration (CUDA) to gain orders of magnitude in speed. I prefer rapid prototyping in PowerShell and then port to C or C# for production, delivering robust, scalable systems for AI-enabled workflows and interoperability with closed-source software. I thrive in remote, high-stakes environments and enjoy mentoring teams and solving hard debugging challenges.…I'm Sean O'Neil, a senior software engineer and information-security expert based in Cairns, Australia. I bring 40+ years of hands-on experience across systems programming, optimisation, reverse engineering, and secure-software architecture. My deep expertise includes C, C++, C#, PowerShell, Intel x86/x64 assembly, compression algorithms, cryptography, and Windows internals. I specialise in reverse engineering closed-source software to recover undocumented file formats, encryption and compression schemes, and communication protocol details to enable interoperability across heterogeneous systems. I've authored cryptographic systems and high-performance algorithms such as PureNoise (IRC encryption, 2000), VEST ciphers (eSTREAM candidates), EnRUPT (NIST SHA-3 candidate). As a former Chief Information Security Officer, I excel at turning complex, slow codepaths into high-performance, low-latency, multi-threaded, vectorised solutions. I'm passionate about extreme software optimization—optimizing CPU cache behaviour, SIMD vectorization, memory layouts, and GPU acceleration (CUDA) to gain orders of magnitude in speed. I prefer rapid prototyping in PowerShell and then port to C or C# for production, delivering robust, scalable systems for AI-enabled workflows and interoperability with closed-source software. I thrive in remote, high-stakes environments and enjoy mentoring teams and solving hard debugging challenges.

Sean O'Neil

Developer, Back-End Developer, Programmer

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I'm Sean O'Neil, a senior software engineer and information-security expert based in Cairns, Australia. I bring 40+ years of hands-on experience across systems programming, optimisation, reverse engineering, and secure-software architecture. My deep expertise includes C, C++, C#, PowerShell, Intel x86/x64 assembly, compression algorithms, cryptography, and Windows internals. I specialise in reverse engineering closed-source software to recover undocumented file formats, encryption and compression schemes, and communication protocol details to enable interoperability across heterogeneous systems. I've authored cryptographic systems and high-performance algorithms such as PureNoise (IRC encryption, 2000), VEST ciphers (eSTREAM candidates), EnRUPT (NIST SHA-3 candidate). As a former Chief Information Security Officer, I excel at turning complex, slow codepaths into high-performance, low-latency, multi-threaded, vectorised solutions. I'm passionate about extreme software optimization—optimizing CPU cache behaviour, SIMD vectorization, memory layouts, and GPU acceleration (CUDA) to gain orders of magnitude in speed. I prefer rapid prototyping in PowerShell and then port to C or C# for production, delivering robust, scalable systems for AI-enabled workflows and interoperability with closed-source software. I thrive in remote, high-stakes environments and enjoy mentoring teams and solving hard debugging challenges.…I'm Sean O'Neil, a senior software engineer and information-security expert based in Cairns, Australia. I bring 40+ years of hands-on experience across systems programming, optimisation, reverse engineering, and secure-software architecture. My deep expertise includes C, C++, C#, PowerShell, Intel x86/x64 assembly, compression algorithms, cryptography, and Windows internals. I specialise in reverse engineering closed-source software to recover undocumented file formats, encryption and compression schemes, and communication protocol details to enable interoperability across heterogeneous systems. I've authored cryptographic systems and high-performance algorithms such as PureNoise (IRC encryption, 2000), VEST ciphers (eSTREAM candidates), EnRUPT (NIST SHA-3 candidate). As a former Chief Information Security Officer, I excel at turning complex, slow codepaths into high-performance, low-latency, multi-threaded, vectorised solutions. I'm passionate about extreme software optimization—optimizing CPU cache behaviour, SIMD vectorization, memory layouts, and GPU acceleration (CUDA) to gain orders of magnitude in speed. I prefer rapid prototyping in PowerShell and then port to C or C# for production, delivering robust, scalable systems for AI-enabled workflows and interoperability with closed-source software. I thrive in remote, high-stakes environments and enjoy mentoring teams and solving hard debugging challenges.

Available to hire

I’m Sean O’Neil, a senior software engineer and information-security expert based in Cairns, Australia. I bring 40+ years of hands-on experience across systems programming, optimisation, reverse engineering, and secure-software architecture. My deep expertise includes C, C++, C#, PowerShell, Intel x86/x64 assembly, compression algorithms, cryptography, and Windows internals. I specialise in reverse engineering closed-source software to recover undocumented file formats, encryption and compression schemes, and communication protocol details to enable interoperability across heterogeneous systems. I’ve authored cryptographic systems and high-performance algorithms such as PureNoise (IRC encryption, 2000), VEST ciphers (eSTREAM candidates), EnRUPT (NIST SHA-3 candidate).

As a former Chief Information Security Officer, I excel at turning complex, slow codepaths into high-performance, low-latency, multi-threaded, vectorised solutions. I’m passionate about extreme software optimization—optimizing CPU cache behaviour, SIMD vectorization, memory layouts, and GPU acceleration (CUDA) to gain orders of magnitude in speed. I prefer rapid prototyping in PowerShell and then port to C or C# for production, delivering robust, scalable systems for AI-enabled workflows and interoperability with closed-source software. I thrive in remote, high-stakes environments and enjoy mentoring teams and solving hard debugging challenges.

Skills

API

Assembly

PowerShell

Experience Level

Expert

Expert

Expert

Expert

Language

English

Fluent

French

Fluent

Russian

Fluent

Work Experience

Inventor / Principal Software Engineer at Raj Global Pty Ltd

August 1, 2025 - Present

Leading the development of ZAP, a next-generation compression engine designed to be 3–60x faster than existing ultra-fast compressors while delivering superior data-type agnosticism. Implemented multi-stage pipeline architecture, entropy models, and high-speed parsing engines; optimized with SSE/AVX across multiple threads and designed optional CUDA-accelerated paths. Oversaw high-precision modelling, AI-based optimisation tools, and compatibility work with initial output in RAR format; proprietary formats are under development. Driving deterministic simulation tools and algorithmic optimisers for patented construction-geometry research and overall software/algorithm design.

Chief Information Security Officer at VoiceValley International

September 1, 2010 - August 1, 2025

Ran security for a large-scale VoIP environment across mixed Windows and Linux infrastructure. Directed secure deployment, audits, intrusion detection, hardening, and cross-border operational continuity. Implemented custom anomaly-detection tooling and DevSecOps pipelines. Led multi-jurisdiction incident response and deep forensic analysis on Windows kernel and Linux servers. Served as top-level technical authority for reverse engineering, exploit mitigation, and secure-architecture. Reverse engineered malicious software and closed-source VoIP components to recover undocumented signaling behavior and transport-layer structures, enabling cross-platform interoperability and robust fraud detection.

Senior Security Researcher / Consultant at Independent & Contract Work

January 1, 1990 - January 1, 2010

Consultant on advanced malware cases for antivirus vendors (including Kaspersky Labs). Conducted research and software development in cryptography and optimization, vulnerability analysis, protocol reversing, and custom tool development. Designed multiple cryptosystems: PureNoise (IRC encryption, 2000), VEST ciphers (eSTREAM candidate), EnRUPT (NIST SHA-3 candidate).

Software Engineer / Systems Architect at Various roles

January 1, 1980 - January 1, 1990

Developed low-level systems, compilers, drivers, and performance-critical software across multiple platforms. Built custom databases, high-performance messaging systems, and early distributed computing frameworks. Conducted extensive reverse engineering across CPU architectures.