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Theo Buehler

PROFILE

Theo Buehler

Worked across openssl/openssl, PowerShell/openssh-portable, curl/curl, and ruby/ruby to deliver robust cryptographic features, cross-platform build improvements, and forward-compatible APIs. Focused on C and assembly language, the work included optimizing OpenBSD arm64 assembly execution, enhancing error handling in cryptographic routines, and introducing new APIs for ASN.1 data structures. Addressed build system reliability by managing submodules and conditional compilation, while refactoring code for maintainability and security. Collaborated on cross-repository upgrades to support OpenSSL 4, improved test coverage, and aligned changes with upstream practices. Emphasized disciplined code review, documentation, and rigorous software testing to ensure long-term stability and integration.

Overall Statistics

Feature vs Bugs

62%Features

Repository Contributions

18Total
Bugs
5
Commits
18
Features
8
Lines of code
1,306
Activity Months8

Your Network

970 people

Work History

February 2026

1 Commits • 1 Features

Feb 1, 2026

February 2026 monthly summary focusing on delivering a high-impact API enhancement in OpenSSL, expanding functionality and improving data integrity, while strengthening test coverage and code quality.

December 2025

9 Commits • 3 Features

Dec 1, 2025

December 2025 monthly summary: Implemented forward-compatibility and encapsulation improvements for ASN.1 handling across curl/curl, ruby/ruby, and openssl/openssl. Focused on reducing build risk with OpenSSL 4, improving security and maintainability, and establishing a solid foundation for future cryptographic updates. Key changes span targeted bug fixes, extensive refactors to opaque ASN1_STRING usage, a new ASN1_BIT_STRING API, and core type-safety improvements. Demonstrated strong cross-repo collaboration and disciplined commit hygiene to deliver cohesive upgrades with clear business value.

October 2025

2 Commits • 1 Features

Oct 1, 2025

October 2025: OpenSSL contributed targeted security and portability improvements with minimal external impact. The changes focus on AArch64 execute-only memory compatibility and robust password-based key derivation error handling, demonstrating strong code quality, cross-platform readiness, and disciplined change management.

July 2025

2 Commits • 1 Features

Jul 1, 2025

July 2025 performance summary for openssl/openssl focused on API accessibility, build stability, and repository hygiene. Delivered a new public API to access TBSCertList signature details, improved build reliability through submodule update, and performed minor housekeeping to maintain codebase cleanliness. These changes reduce downstream integration risk, improve maintainability, and demonstrate strong cross-functional tooling and testing practices.

April 2025

1 Commits

Apr 1, 2025

April 2025 monthly summary for PowerShell/openssh-portable focused on eliminating build-time issues and strengthening cross-platform reliability. Implemented DSA-related gating to ensure clean builds when DSA is disabled, updated header version metadata, and validated compilation across configurations. This work reduces build failures in environments without DSA, eases integration, and improves maintainability.

March 2025

1 Commits

Mar 1, 2025

March 2025: Delivered a critical cryptographic robustness improvement in the OpenSSH client within the PowerShell/openssh-portable repository. Implemented robust EVP_CIPHER_CTX_ctrl() return value handling to treat non-positive results as errors, preventing misinterpretation of cryptographic operation failures and increasing overall SSH reliability. This work reduces risk of silent failures in encryption workflows and enhances client-side cryptographic robustness. Overall impact: improved reliability and security of SSH operations with a minimal, focused change to the cryptographic control flow. The change supports stable business operations that rely on secure remote access and file transfer. Technologies/skills demonstrated: C cryptographic API handling, rigorous error-checking, upstream-first fix workflow, and contribution discipline (code review, commit hygiene, and traceability).

December 2024

1 Commits • 1 Features

Dec 1, 2024

December 2024: Focused maintenance in PowerShell/openssh-portable. Implemented code cleanup in sshkey.c by removing redundant checks for prime-field definitions and eliminating the EC_GROUP_method_of() call, enabling easier future refactoring and aligning with upstream OpenSSH practices. No major bugs fixed this month; the work reduces complexity and maintenance risk, improving long-term stability and readiness for future feature work.

April 2024

1 Commits • 1 Features

Apr 1, 2024

OpenBSD arm64 assembly execution and build compatibility implemented for OpenSSL, enabling assembly code execution on OpenBSD arm64 by relocating constants to .rodata and updating assembler scripts to align with OpenSSL's build process. This work improves cross-platform portability and reduces platform-specific build issues for arm64.

Activity

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Quality Metrics

Correctness97.8%
Maintainability95.6%
Architecture95.6%
Performance93.4%
AI Usage20.0%

Skills & Technologies

Programming Languages

AssemblyCPerlRubySubmodule

Technical Skills

API DevelopmentAPI developmentAssembly language optimizationBuild System ManagementBuild SystemsC ProgrammingC programmingCode RefactoringCryptographyDocumentationEmbedded systemsLow-level programmingOpenBSDOpenBSD DevelopmentOpenSSL

Repositories Contributed To

4 repos

Overview of all repositories you've contributed to across your timeline

openssl/openssl

Apr 2024 Feb 2026
5 Months active

Languages Used

AssemblyPerlCSubmodule

Technical Skills

OpenBSDassembly languagecross-platform developmentlow-level programmingAPI DevelopmentBuild System Management

ruby/ruby

Dec 2025 Dec 2025
1 Month active

Languages Used

CRuby

Technical Skills

API developmentC programmingCryptographyOpenSSLOpenSSL integrationRuby development

PowerShell/openssh-portable

Dec 2024 Apr 2025
3 Months active

Languages Used

C

Technical Skills

Code RefactoringCryptographyOpenBSD DevelopmentC ProgrammingOpenSSL APIBuild Systems

curl/curl

Dec 2025 Dec 2025
1 Month active

Languages Used

C

Technical Skills

C programmingSSL/TLScryptography