Commented code of a uint128 subtraction using TFHE-rs C API.
The following example demonstrates uint128 subtraction using the TFHE-rs C API:
WARNING: this example omits proper memory management in the error case to improve code readability.
Ensure the above CMakeLists.txt and main.c files are in the same directory. Use the following commands to execute the example:
# /!\ Be sure to update CMakeLists.txt to give the absolute path to the compiled tfhe library$lsCMakeLists.txtmain.c$mkdirbuild&&cdbuild$cmake..-DCMAKE_BUILD_TYPE=RELEASE...$make...$./my-executableFHEcomputationsuccessful!$
#include"tfhe.h"#include<assert.h>#include<stdio.h>intmain(void){int ok =0;// Prepare the config builder for the high level API and choose which types to enable ConfigBuilder *builder; Config *config;// Put the builder in a default state without any types enabledconfig_builder_default(&builder);// Use the small LWE key for encryptionconfig_builder_default_with_small_encryption(&builder);// Populate the configconfig_builder_build(builder,&config); ClientKey *client_key =NULL; ServerKey *server_key =NULL;// Generate the keys using the configgenerate_keys(config,&client_key,&server_key);// Set the server key for the current threadset_server_key(server_key); FheUint128 *lhs =NULL; FheUint128 *rhs =NULL; FheUint128 *result =NULL;// A 128-bit unsigned integer containing value: 20 << 64 | 10 U128 clear_lhs = { .w0 =10, .w1 =20 };// A 128-bit unsigned integer containing value: 2 << 64 | 1 U128 clear_rhs = { .w0 =1, .w1 =2 }; ok =fhe_uint128_try_encrypt_with_client_key_u128(clear_lhs, client_key,&lhs);assert(ok ==0); ok =fhe_uint128_try_encrypt_with_client_key_u128(clear_rhs, client_key,&rhs);assert(ok ==0);// Compute the subtraction ok =fhe_uint128_sub(lhs, rhs,&result);assert(ok ==0); U128 clear_result;// Decrypt ok =fhe_uint128_decrypt(result, client_key,&clear_result);assert(ok ==0);// Here the subtraction allows us to compare each wordassert(clear_result.w0 ==9);assert(clear_result.w1 ==18);// Destroy the ciphertextsfhe_uint128_destroy(lhs);fhe_uint128_destroy(rhs);fhe_uint128_destroy(result);// Destroy the keysclient_key_destroy(client_key);server_key_destroy(server_key);printf("FHE computation successful!\n");return EXIT_SUCCESS;}