Architecture

Stoffel VM is a register based virtual machine with two sets of registers. Clear registers for manipulating non-secret values. Secret registers are used for manipulating secret values.

Technical Overview

Virtual Machine Architecture

  • What type of VM is stoffel
  • Clear vs Secret values

Instruction Set

  • Complete reference of supported VM instructions
  • Opcode specifications and behavior
  • Optimization opportunities

Builtin Types

  • Overview of core data types (numbers, strings, arrays, etc.)
  • Type conversion and manipulation
  • Memory representation and optimization

Activation Records

  • Call stack management and function invocation
  • Local variable scoping and lifetime
  • Optimizing stack frame allocation

VM Functions

  • Virtual machine architecture overview
  • Execution model and stack management
  • Error handling

Closures Overview

  • Lexical scoping and variable capture
  • Implementation details and memory management

Foreign Function Interface

  • Integrating with external libraries and systems
  • Data marshalling and type conversion
  • Performance considerations for FFI calls

Builtin Methods

  • Standard library functions and utilities
  • Common operations for each data type

Runtime Hooks

  • Extension points for monitoring and customization
  • Performance profiling and instrumentation
  • Debugging facilities

Why a Register Machine?

The choice of a register-based architecture over a stack-based design was driven by several key factors:

  1. Parallelization Opportunities

    • Register machines allow for easier identification of independent instructions
    • Multiple instructions can be executed in parallel, reducing overall execution time
    • Better suited for modern hardware architectures

  2. Communication Efficiency

    • Reduced number of memory access operations
    • Fewer rounds of communication in Multi-Party Computation (MPC) contexts
    • More efficient instruction encoding

  3. Optimization Potential

    • Direct access to operands enables better optimization strategies
    • Easier to implement specialized instructions
    • More straightforward analysis of data flow

Why dedicated clear and secret registers

  1. Implicit reveal and hide
    • Having dedicated registers for secret and clear values allows us to implicitly reveal and hide values as they're moved between registers.
    • Separation of registers allows for optimizations to be applied specifically to clear or secret operations.
    • Avoids having to track the type of the virtual register during runtime as values may become secret shared or reveal through the course of execution.