# WARNING
This is a modified version of Emp-tool that was cloned on August 1st 2022. This library was modified to use SHA256 instead of SHA3 for circuit computations to make it easier to use with BoringSSL. 

# emp-tool
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<img src="https://raw.githubusercontent.com/emp-toolkit/emp-readme/master/art/logo-full.jpg" width=300px/>



# Installation
1. `wget https://raw.githubusercontent.com/emp-toolkit/emp-readme/master/scripts/install.py`
2. `python install.py --deps --tool `
    1. You can use `--ot=[release]` to install a particular branch or release
    2. By default it will build for Release. `-DCMAKE_BUILD_TYPE=[Release|Debug]` option is also available.
    3. No sudo? Change [`CMAKE_INSTALL_PREFIX`](https://cmake.org/cmake/help/v2.8.8/cmake.html#variable%3aCMAKE_INSTALL_PREFIX).


# Usage

## Basic Primitives
### Pseudorandom generator
PRG is implemented as AES-NI in the CTR mode. Usage is presented as the following code sample.

```cpp
#include<emp-tool/emp-tool.h>
using namespace emp;
PRG prg;//using a secure random seed

int rand_int, rand_ints[100];
block rand_block[3];

prg.random_data(&rand_int, sizeof(rand_int)); //fill rand_int with 32 random bits
prg.random_block(rand_block, 3);	      //fill rand_block with 128*3 random bits

prg.reseed(&rand_block[1]);                   //reset the seed and counter in prg
prg.random_data_unaligned(rand_ints+2, sizeof(int)*98);  //when the array is not 128-bit-aligned
```

### Pseudorandom permutation
PRP is implemented based on AES-NI. Code sample:
```cpp
block key;
PRG().random_block(&key,1)
PRP prp(key); //if no parameter is provided, a public, fixed key will be used

block rand_block[3], b3[3];
int rand_ints[100];

prp.permute_block(rand_block, 3);//applying pi on each block of data
prp.permute_data(rand_ints, sizeof(int)*100);

block b2 = prp.H(rand_block[1], 1); //b2 = pi(r)\xor r, where r = doubling(random_block)\xor 1

prp.H<3>(b3, rand_block, 0);// apply the above H on three blocks using counter 0, 1, and 2 resp.
```

### Hash function
Essentially a wrapper of ```<openssl/sha.h>```
```cpp
Hash hash;

char * data = new char[1024*1024], dig[Hash::DIGEST_SIZE];

hash.put(data, 1024*1024);
hash.digest(dig);
```

### Commitment
```cpp
Commitment c;

char * data = new char[1024*1024];
Com com;
Decom decom;

c.commit(decom, com, data, 1024*1024); // commit, will fill values decom and com
assert(c.open(decom, com, data, 1024*1024)); // open, return if the decommitment is valid or not
```

## On-the-fly Circuit Compiler


## [Acknowledgement, Reference, and Questions](https://github.com/emp-toolkit/emp-readme/blob/master/README.md#citation)

