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Input/Output

This section gives an overview over the input/output facilities.

Private Inputs from Computing Parties

All secret types have an input function (e.g. :pyCompiler.types.sint.get_input_from or :pyCompiler.types.sfix.get_input_from). Inputs are read as whitespace-separated text in order (independent of the data type) from Player-Data/Input-P<player>-<thread>, where thread is 0 for the main thread. You can change the prefix (Player-Data/Input) using the -IF option on the virtual machine binary. You can also use -I to read inputs from the command line. :pyCompiler.types.sint.input_tensor_from and :pyCompiler.types.sfix.input_tensor_from allow inputting a tensor.

Compile-Time Data via Private Input

:py~Compiler.types.sint.input_tensor_via is a convenience function that allows to use data available at compile-time via private input.

Public Inputs

All types can be assigned a hard-coded value at compile time, e.g. sint(1). This is impractical for larger amounts of data. :py~Compiler.library.foreach_enumerate provides a facility for this case. It uses :py~Compiler.library.public_input internally, which reads from Programs/Public-Input/<progname>.

Public Outputs

By default, :py~Compiler.library.print_ln and related functions only output to the terminal on party 0. This allows to run several parties in one terminal without spoiling the output. You can use interactive mode with option -I in order to output on all parties. Note that this also to reading inputs from the command line unless you specify -IF as well. You can also specify a file prefix with -OF, so that outputs are written to <prefix>-P<player>-<thread>.

Private Outputs to Computing Parties

Some types provide a function to reveal a value only to a specific party (e.g., :pyCompiler.types.sint.reveal_to). It can be used conjunction with :py~Compiler.library.print_ln_to in order to output it.

Binary Output

Most types returned by :pyreveal or :pyreveal_to feature a :pybinary_output method, which writes to Player-Data/Binary-Output-P<playerno>-<threadno>. The format is either signed 64-bit integer or double-precision floating-point in machine byte order (usually little endian).

Clients (Non-computing Parties)

:pyCompiler.types.sint.receive_from_client and :pyCompiler.types.sint.reveal_to_clients allow communicating securely with the clients. See this example covering both client code and server-side high-level code. :pyCompiler.types.sint.input_tensor_from_client and :pyCompiler.types.MultiArray.reveal_to_clients. The same functions are available for :py~Compiler.types.sfix and :py~Compiler.types.Array, respectively. See also client ref below.

Secret Shares

:pyCompiler.types.sint.read_from_file and :pyCompiler.types.sint.write_to_file allow reading and writing secret shares to and from files. These instructions use Persistence/Transactions-P<playerno>.data. The format depends on the protocol with the following principles.

  • One share follows the other without metadata.
  • If there is a MAC, it comes after the share.
  • Numbers are stored in little-endian format.
  • Numbers modulo a power of two are stored with the minimal number of bytes.
  • Numbers modulo a prime are stored in Montgomery representation in blocks of eight bytes.

Another possibility for persistence between program runs is to use the fact that the memory is stored in Player-Data/Memory-<protocol>-P<player> at the end of a run. The best way to use this is via the memory access functions like :py~Compiler.types.sint.store_in_mem and :py~Compiler.types.sint.load_mem. Make sure to only use addresses below USER_MEM specified in Compiler/config.py to avoid conflicts with the automatic allocation used for arrays etc. Note also that all types based on :py~Compiler.types.sint (e.g., :py~Compiler.types.sfix) share the same memory, and that the address is only a base address. This means that vectors will be written to the memory starting at the given address.

Reference

Client