mpc

Secure Multi-Party Computation with Go. This project implements secure two-party computation with Garbled circuit protocol. The main components are:

• garbled: command-line program for running MPCL programs
• compiler: Multi-Party Computation Language (MPCL) compiler
• circuit: garbled circuit parser, garbler, and evaluator
• ot: oblivious transfer library

Getting started

The easiest way to experiment with the system is to compile the garbled application and use it to evaluate MPCL programs. The garbled application takes the following command line options:

• -O: optimization level (default 1 enabling all current optimizations).
• -circ: compile inputs to circuit format.
• -cpuprofile: write cpu profile to the specified file.
• -d: enable diagnostics outputs.
• -dot: generate Graphviz DOT output.
• -e: specifies circuit evaluator / garbler mode. The circuit evaluator creates a TCP listener and waits for garblers to connect with computation.
• -format: specifies circuit format for the -circ output file. Possible values are: mpclc (default), bristol.
• -i: specifies comma-separated input values for the circuit.
• -memprofile: write memory profile to the specified file.
• -ssa: compile MPCL input to SSA assembly.
• -stream: streaming mode.
• -v: enabled verbose output.

The examples directory contains various MPCL example programs which can be executed with the garbled application. For example, here's how you can run the Yao's Millionaires' Problem which can be found from the millionaire.mpcl file:

package main

func main(a, b int64) bool {
    if a > b {
        return true
    } else {
        return false
    }
}

First, start the evaluator (these examples are run in the apps/garbled directory):

$ ./garbled -e -i 800000 examples/millionaire.mpcl
 - In1: a{1,0}i64:int64
 + In2: b{1,0}i64:int64
 - Out: %_{0,1}b1:bool1
 -  In: [800000]
Listening for connections at :8080

The evaluator's input is 800000 and it is set to the circuit inputs In2. The evaluator is now waiting for garblers to connect to the TCP port :8080.

Next, let's start the garbler:

$ ./garbled -i 750000 examples/millionaire.mpcl
 + In1: a{1,0}i64:int64
 - In2: b{1,0}i64:int64
 - Out: %_{0,1}b1:bool1
 -  In: [750000]
Result[0]: false

The garbler's input is 750000 and it is set to the circuit inputs In1. The garbler connects to the evaluator's TCP port and they run the garbled circuit protocol. At the end, garbler (and evaluator) print the result of the circuit, which is this case is single bool value Result[0]:

Result[0]: false

In our example, the evaluator's argument In2 is bound to the MPCL program's b int64 argument, and garbler's In1 to a int64. Therefore, the result of the computation is false because In1=750000 <= In2=800000. If we increase the garbler's input to 900000, we see that the result is now true since the garbler's input is now bigger than the evaluator's input:

$ ./garbled -i 900000 examples/millionaire.mpcl
 + In1: a{1,0}i64:int64
 - In2: b{1,0}i64:int64
 - Out: %_{0,1}b1:bool1
 -  In: [900000]
Result[0]: true

Ed25519 Key Generation and Signature Computation

The ed25519 directory contains Ed25519 key generation and signature computation examples.

Key Generation

$ ./garbled -stream -e -v -i 0x784db0ec4ca0cf5338249e6a09139109366dca1fac2838e5f0e5a46f0e191bae,0xd0da45d3c99e756da831d1e7d696eae3fa9fe39d3b1b2618c7ff997d17777989b5cf415b114298c8b10bed0f0eff118e43ab606ab01143151dff89171307dffa,0x44bf09357e19b1f96f9cf6d9e7d25a0e8dd62d6e0d4bba2bec4c59983c7dc84d1486677b6d8837746cd948c881913c36faeaee08e8309afac58be4757a1c544e

$ ./garbled -stream -v -i 0x57c0e59c20ac7d75ef7e3188fdd7f5876abee1cab394af8125acaca9760bb54c,0x76b42e6292f4a3dc339d208481abeb9a24e08127c7cd8dbde62abcddc0c0e6f7a0f740e756b44dae137f0e7ff8eae0ceb1a962c130fdcbe8cbee3e31ab55b8dc,0xeb83eb1f5203f5b752c96264a21ff4a27fa60cf2313f5f53c3fa96e0b52a2814b786e43a3af64b66291b5b29f432cb8d5a930e31f4e6f072a6d33b861b5b5f13 examples/ed25519/keygen.mpcl
┏━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━┳━━━━━━━━┳━━━━━━┓
┃ Op          ┃            Time ┃      % ┃ Xfer ┃
┡━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━╇━━━━━━━━╇━━━━━━┩
│ Init        │      2.039289ms │  0.00% │   0B │
│ OT Init     │    248.443521ms │  0.27% │ 21kB │
│ Peer Inputs │   10.330183787s │ 11.10% │  1MB │
│ Eval        │ 1m22.462325965s │ 88.63% │ 14GB │
│ Total       │ 1m33.042992562s │        │ 14GB │
└─────────────┴─────────────────┴────────┴──────┘
Max permanent wires: 52138674, cached circuits: 23
#gates=824319227 (XOR=529672017 XNOR=28633983 AND=265892049 OR=116232 INV=4946 xor=558306000 !xor=266013227) #w=847060405
Result[0]: 8ae64963506002e267a59665e9a2e6f9348cc159be53747894478e182ece9fcb
Result[1]: 4ded80ae09692306c9659307f522f5dba1d96e48cde9f4f6e22fb340629db76aa2bee5867d009e008b6fb85902273acda8910c9a740a788f70c28ca0a3093835
Result[2]: cd5c37f4497fd56e236aa858442b3ff90f7a6401ee2186ea18d074fe93d8f9d18b582fa47a1ee0f0a9083ddd9e262b8f3c642dfad68f667f87dddd4bec80aca3

Signature Computation

$ ./garbled -stream -e -v -i 0x46eb82a021d88960fb13388b0e76ba13b84524ffe114d7f3a728b39efc185eeaa7137132182bab7504daf200d882b787ee8b9b1c9f41be9c38fb4e0ba1aff326

$ ./garbled -stream -v -i 0x4d61726b6b7520526f737369203c6d747240696b692e66693e2068747470733a2f2f7777772e6d61726b6b75726f7373692e636f6d2f,0x5e768ad83640b43d93d6c26b34021d0a0cda6bf5eb962970554d7ab074e2f4cd49bc6fef2fa4dc2f763c1f70b751b7f03d398e8930d837130426454ea52d4449 examples/ed25519/sign.mpcl
┏━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━┳━━━━━━━━┳━━━━━━━┓
┃ Op          ┃            Time ┃      % ┃  Xfer ┃
┡━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━╇━━━━━━━━╇━━━━━━━┩
│ Init        │      1.303611ms │  0.00% │    0B │
│ OT Init     │    131.270606ms │  0.15% │  16kB │
│ Peer Inputs │    4.123998305s │  4.69% │ 667kB │
│ Eval        │ 1m23.745891208s │ 95.16% │  15GB │
│ Total       │  1m28.00246373s │        │  15GB │
└─────────────┴─────────────────┴────────┴───────┘
Max permanent wires: 53913890, cached circuits: 25
#gates=830082709 (XOR=533261481 XNOR=28815787 AND=267491441 OR=494216 INV=19784 xor=562077268 !xor=268005441) #w=853799279
Result[0]: b71a55aece64574bedd94729a9ca95a87b5fe0a587fecf50ff0238805132c1291e08cb871016cb4f3935bd45423626f61dc648a91affda3671b19d7b28e03505

Multi-Party Computation Language (MPCL)

The multi-party computation language is heavily inspired by the Go programming language, however it is not using the Go's compiler or any other related components. The compiler is an independent implementation of the relevant parts of the Go syntax.

Builtin functions

The MPCL runtime defines the following builtin functions:

• copy(dst, src): copies the content of the array src to dst. The function returns the number of elements copied, which is the minimum of len(src) and len(dst).
• len(value): returns the length of the value as integer:
  • array: returns the number of array elements
  • string: returns the number of bytes in the string
• make(type, size): creates an instance of the type type with size bits.
• native(name, arg...): calls a builtin function name with arguments arg.... The name can specify a circuit file (*.circ) or one of the following builtin functions:
  • hamming(a, b uint) computes the bitwise hamming distance between argument values
• size(variable): returns the bit size of the argument variable.

TODO

• Foundation
  • Circuit & garbling:
    • Oblivious transfer extensions
    • SSA variable liveness analysis must be optimized
  • TLS for garbler-evaluator protocol
  • BMR multi-party protocol
• Compiler
  • Check that types.Rune is used consistently.
  • Incremental compiler
    • Constant folding
      • Implement using AST rewrite
      • binary expressions
      • if-blocks
      • For-loop unrolling
      • Function call and return
    • peephole optimization
      • SSA aliasing is 1:1 but amov has 2:1 relation
      • variable liveness analysis for templates
    • BitShift
  • copy() does not work on arrays which have been make():ed
  • &base[pos][i] returns the address of the first element
  • reading from *[32]int32 returns invalid values
  • Pointer handling
    • Cleanup pointer r-value handling
    • Slices are passed by value instead of by reference
    • Selecting struct members from struct pointer value
• Streamer
  • Uninitialized variables produce unspecified values in stream mode
• Ed25519
  • Parsing Ed25519 MPCL files
    • local variables in for-loop unrolling
  • Compound init values must be zero-padded to full size

Circuit Optimization

Optimizations from stevengoldfeder.com:

File	No. ANDs	No. XORs	No. INVs
Our circuit	sha256Final.txt	22,272	91,780	2,194
Bristol circuit	sha-256.txt	90,825	42,029	103,258

Benchmarks and tests

Please, see the benchmarks.md file for information about various benchmarks.