private UInt32 ComputeSum(MapperProgram program, UInt32 row_min, UInt32 row_max, UInt32 answer_units,
UInt32 answer_min, UInt32 answer_max)
{
UInt32 clipped_scaled_sum = 0;
UInt32 total_remainder = 0;
foreach (DiffPrivRow row in rows)
{
UInt32 row_value = program.Run(row.data);
UInt32 clipped_value = ClipWord32(row_value, row_min, row_max);
UInt32 scaled_value = clipped_value / answer_units;
UInt32 scaling_remainder = clipped_value % answer_units;
clipped_scaled_sum = SaturatingAdd(clipped_scaled_sum, scaled_value);
total_remainder = total_remainder + scaling_remainder;
if (total_remainder >= answer_units)
{
clipped_scaled_sum = SaturatingAdd(clipped_scaled_sum, 1);
total_remainder -= answer_units;
}
}
UInt32 extra = (UInt32)(total_remainder * 2 >= answer_units ? 1 : 0);
clipped_scaled_sum = SaturatingAdd(clipped_scaled_sum, extra);
return(ClipWord32(clipped_scaled_sum, answer_min, answer_max));
}
public byte[] HandleQueryRequest(QueryRequest request)
{
if (request.row_min > request.row_max)
{
Console.Error.WriteLine("Row value range empty");
return(DiffPrivSrvResponse.EncodeQueryResponse(1, 0));
}
if (request.answer_min > request.answer_max)
{
Console.Error.WriteLine("Answer range empty");
return(DiffPrivSrvResponse.EncodeQueryResponse(2, 0));
}
if (request.answer_units <= 0)
{
Console.Error.WriteLine("Answer units not positive");
return(DiffPrivSrvResponse.EncodeQueryResponse(3, 0));
}
if (request.alpha_num <= request.alpha_den)
{
Console.Error.WriteLine("Alpha not greater than 1");
return(DiffPrivSrvResponse.EncodeQueryResponse(6, 0));
}
if (request.beta_num <= request.beta_den)
{
Console.Error.WriteLine("Beta not greater than 1");
return(DiffPrivSrvResponse.EncodeQueryResponse(13, 0));
}
UInt32[] program_words = CommonRoutines.BEByteSeqToWordSeq(request.program_encoding);
MapperProgram program = new MapperProgram(program_words);
if (!program.IsValid())
{
Console.Error.WriteLine("Invalid program provided for query");
return(DiffPrivSrvResponse.EncodeQueryResponse(4, 0));
}
if (request.answer_units >= 0x80000000)
{
Console.Error.WriteLine("Answer granularity too high");
return(DiffPrivSrvResponse.EncodeQueryResponse(17, 0));
}
BigRational alpha = new BigRational(request.alpha_num, request.alpha_den);
BigRational beta = new BigRational(request.beta_num, request.beta_den);
UInt32 delta = DivideRoundingUp(request.row_max - request.row_min, request.answer_units);
UInt32 B = request.answer_max - request.answer_min;
if (B <= 0)
{
Console.Error.WriteLine("Answer range empty");
return(DiffPrivSrvResponse.EncodeQueryResponse(5, 0));
}
if (alpha <= new BigRational(1))
{
return(DiffPrivSrvResponse.EncodeQueryResponse(6, 0));
}
BigRational alpha_to_delta = BigRational.Power(alpha, delta);
if (beta <= alpha_to_delta)
{
Console.Error.WriteLine("Beta not greater than alpha to the power of delta");
return(DiffPrivSrvResponse.EncodeQueryResponse(7, 0));
}
if (beta > budget)
{
Console.Error.WriteLine("Not enough budget for request");
return(DiffPrivSrvResponse.EncodeQueryResponse(11, 0));
}
BigRational one = new BigRational(1);
BigRational two = new BigRational(2);
BigRational min_alpha_minus_1_and_2 = alpha - one;
if (min_alpha_minus_1_and_2 > two)
{
min_alpha_minus_1_and_2 = two;
}
BigRational noiseEntropyPart1 = (alpha + one) * (beta + one) / ((beta - alpha_to_delta) * min_alpha_minus_1_and_2);
UInt32 r1;
if (!FindHigherPowerOfTwo(noiseEntropyPart1, out r1) || r1 >= 0xFFFFFFE0)
{
Console.Error.WriteLine("Requires too many bits of randomness due to noise entropy part 1");
return(DiffPrivSrvResponse.EncodeQueryResponse(8, 0));
}
UInt32 log_alpha;
if (!FindHigherPowerOfTwo(alpha, out log_alpha) || log_alpha > 0xFFFFFFFFUL / B)
{
Console.Error.WriteLine("Requires too many bits of randomness due to alpha");
return(DiffPrivSrvResponse.EncodeQueryResponse(8, 0));
}
UInt32 r2 = log_alpha * (B - 1);
if (r2 >= 0xFFFFFFC8 - r1)
{
Console.Error.WriteLine("Requires too many bits of randomness due to r2");
return(DiffPrivSrvResponse.EncodeQueryResponse(8, 0));
}
UInt32 r = RoundUpToMultiple(r1 + r2 + 7, 8);
UInt32 num_randoms_needed = RoundUpToMultiple(r / 8, 4) + 1;
bool negate_noise = (rng.Next() % 2 == 0);
byte[] randoms = new byte[num_randoms_needed];
rng.NextBytes(randoms);
randoms[num_randoms_needed - 1] = 0;
BigInteger U = new BigInteger(randoms);
BigRational one_half = new BigRational(1, 2);
BigRational numerator = new BigRational(U) + one_half;
BigRational denominator = BigRational.Power(two, (num_randoms_needed - 1) * 8);
BigRational u = numerator / denominator;
BigRational threshold = (two * alpha) / (u * (alpha + one));
UInt32 absolute_noise = FindHighestPowerLeThreshold(alpha, threshold, B);
UInt32 answer = ComputeSum(program, request.row_min, request.row_max, request.answer_units, request.answer_min, request.answer_max);
UInt32 noised_answer = AddNoise(answer, absolute_noise, negate_noise);
UInt32 response = ClipWord32(noised_answer, request.answer_min, request.answer_max);
budget = budget / beta;
return(DiffPrivSrvResponse.EncodeQueryResponse(0, response));
}
public byte[] HandleQueryRequest(QueryRequest request)
{
if (request.row_min > request.row_max)
{
Console.Error.WriteLine("Row value range empty");
return DiffPrivSrvResponse.EncodeQueryResponse(1, 0);
}
if (request.answer_min > request.answer_max)
{
Console.Error.WriteLine("Answer range empty");
return DiffPrivSrvResponse.EncodeQueryResponse(2, 0);
}
if (request.answer_units <= 0)
{
Console.Error.WriteLine("Answer units not positive");
return DiffPrivSrvResponse.EncodeQueryResponse(3, 0);
}
if (request.alpha_num <= request.alpha_den)
{
Console.Error.WriteLine("Alpha not greater than 1");
return DiffPrivSrvResponse.EncodeQueryResponse(6, 0);
}
if (request.beta_num <= request.beta_den)
{
Console.Error.WriteLine("Beta not greater than 1");
return DiffPrivSrvResponse.EncodeQueryResponse(13, 0);
}
UInt32[] program_words = CommonRoutines.BEByteSeqToWordSeq(request.program_encoding);
MapperProgram program = new MapperProgram(program_words);
if (!program.IsValid())
{
Console.Error.WriteLine("Invalid program provided for query");
return DiffPrivSrvResponse.EncodeQueryResponse(4, 0);
}
if (request.answer_units >= 0x80000000)
{
Console.Error.WriteLine("Answer granularity too high");
return DiffPrivSrvResponse.EncodeQueryResponse(17, 0);
}
BigRational alpha = new BigRational(request.alpha_num, request.alpha_den);
BigRational beta = new BigRational(request.beta_num, request.beta_den);
UInt32 delta = DivideRoundingUp(request.row_max - request.row_min, request.answer_units);
UInt32 B = request.answer_max - request.answer_min;
if (B <= 0)
{
Console.Error.WriteLine("Answer range empty");
return DiffPrivSrvResponse.EncodeQueryResponse(5, 0);
}
if (alpha <= new BigRational(1))
{
return DiffPrivSrvResponse.EncodeQueryResponse(6, 0);
}
BigRational alpha_to_delta = BigRational.Power(alpha, delta);
if (beta <= alpha_to_delta)
{
Console.Error.WriteLine("Beta not greater than alpha to the power of delta");
return DiffPrivSrvResponse.EncodeQueryResponse(7, 0);
}
if (beta > budget)
{
Console.Error.WriteLine("Not enough budget for request");
return DiffPrivSrvResponse.EncodeQueryResponse(11, 0);
}
BigRational one = new BigRational(1);
BigRational two = new BigRational(2);
BigRational min_alpha_minus_1_and_2 = alpha - one;
if (min_alpha_minus_1_and_2 > two)
{
min_alpha_minus_1_and_2 = two;
}
BigRational noiseEntropyPart1 = (alpha + one) * (beta + one) / ((beta - alpha_to_delta) * min_alpha_minus_1_and_2);
UInt32 r1;
if (!FindHigherPowerOfTwo(noiseEntropyPart1, out r1) || r1 >= 0xFFFFFFE0)
{
Console.Error.WriteLine("Requires too many bits of randomness due to noise entropy part 1");
return DiffPrivSrvResponse.EncodeQueryResponse(8, 0);
}
UInt32 log_alpha;
if (!FindHigherPowerOfTwo(alpha, out log_alpha) || log_alpha > 0xFFFFFFFFUL / B)
{
Console.Error.WriteLine("Requires too many bits of randomness due to alpha");
return DiffPrivSrvResponse.EncodeQueryResponse(8, 0);
}
UInt32 r2 = log_alpha * (B-1);
if (r2 >= 0xFFFFFFC8 - r1)
{
Console.Error.WriteLine("Requires too many bits of randomness due to r2");
return DiffPrivSrvResponse.EncodeQueryResponse(8, 0);
}
UInt32 r = RoundUpToMultiple(r1 + r2 + 7, 8);
UInt32 num_randoms_needed = RoundUpToMultiple(r / 8, 4) + 1;
bool negate_noise = (rng.Next() % 2 == 0);
byte[] randoms = new byte[num_randoms_needed];
rng.NextBytes(randoms);
randoms[num_randoms_needed - 1] = 0;
BigInteger U = new BigInteger(randoms);
BigRational one_half = new BigRational(1, 2);
BigRational numerator = new BigRational(U) + one_half;
BigRational denominator = BigRational.Power(two, (num_randoms_needed - 1) * 8);
BigRational u = numerator / denominator;
BigRational threshold = (two * alpha) / (u * (alpha + one));
UInt32 absolute_noise = FindHighestPowerLeThreshold(alpha, threshold, B);
UInt32 answer = ComputeSum(program, request.row_min, request.row_max, request.answer_units, request.answer_min, request.answer_max);
UInt32 noised_answer = AddNoise(answer, absolute_noise, negate_noise);
UInt32 response = ClipWord32(noised_answer, request.answer_min, request.answer_max);
budget = budget / beta;
return DiffPrivSrvResponse.EncodeQueryResponse(0, response);
}
private UInt32 ComputeSum (MapperProgram program, UInt32 row_min, UInt32 row_max, UInt32 answer_units,
UInt32 answer_min, UInt32 answer_max)
{
UInt32 clipped_scaled_sum = 0;
UInt32 total_remainder = 0;
foreach (DiffPrivRow row in rows)
{
UInt32 row_value = program.Run(row.data);
UInt32 clipped_value = ClipWord32(row_value, row_min, row_max);
UInt32 scaled_value = clipped_value / answer_units;
UInt32 scaling_remainder = clipped_value % answer_units;
clipped_scaled_sum = SaturatingAdd(clipped_scaled_sum, scaled_value);
total_remainder = total_remainder + scaling_remainder;
if (total_remainder >= answer_units)
{
clipped_scaled_sum = SaturatingAdd(clipped_scaled_sum, 1);
total_remainder -= answer_units;
}
}
UInt32 extra = (UInt32)(total_remainder * 2 >= answer_units ? 1 : 0);
clipped_scaled_sum = SaturatingAdd(clipped_scaled_sum, extra);
return ClipWord32(clipped_scaled_sum, answer_min, answer_max);
}