/// <summary>
/// Creates an instance of SEALContext and performs several pre-computations
/// on the given EncryptionParameters.
/// </summary>
/// <param name="parms">The encryption parameters.</param>
/// <param name="expandModChain">Determines whether the modulus switching chain
/// should be created</param>
/// <param name="secLevel">Determines whether a specific security level should be
/// enforced according to HomomorphicEncryption.org security standard</param>
/// <exception cref="ArgumentNullException">if parms is null</exception>
public SEALContext(EncryptionParameters parms,
bool expandModChain = true, SecLevelType secLevel = SecLevelType.TC128)
{
if (null == parms)
{
throw new ArgumentNullException(nameof(parms));
}
NativeMethods.SEALContext_Create(parms.NativePtr,
expandModChain, (int)secLevel, out IntPtr context);
NativePtr = context;
}
/// <summary>
/// Returns a default coefficient modulus for the BFV scheme that guarantees
/// a given security level when using a given PolyModulusDegree, according
/// to the HomomorphicEncryption.org security standard.
/// </summary>
/// <remarks>
/// <para>
/// Returns a default coefficient modulus for the BFV scheme that guarantees
/// a given security level when using a given PolyModulusDegree, according
/// to the HomomorphicEncryption.org security standard. Note that all security
/// guarantees are lost if the output is used with encryption parameters with
/// a mismatching value for the PolyModulusDegree.
/// </para>
/// <para>
/// The coefficient modulus returned by this function will not perform well
/// if used with the CKKS scheme.
/// </para>
/// </remarks>
/// <param name="polyModulusDegree">The value of the PolyModulusDegree
/// encryption parameter</param>
/// <param name="secLevel">The desired standard security level</param>
/// <exception cref="ArgumentException">if polyModulusDegree is not
/// a power-of-two or is too large</exception>
/// <exception cref="ArgumentException">if secLevel is SecLevelType.None</exception>
static public IEnumerable <Modulus> BFVDefault(
ulong polyModulusDegree, SecLevelType secLevel = SecLevelType.TC128)
{
List <Modulus> result = null;
ulong length = 0;
NativeMethods.CoeffModulus_BFVDefault(polyModulusDegree, (int)secLevel, ref length, null);
IntPtr[] coeffArray = new IntPtr[length];
NativeMethods.CoeffModulus_BFVDefault(polyModulusDegree, (int)secLevel, ref length, coeffArray);
result = new List <Modulus>(checked ((int)length));
foreach (IntPtr sm in coeffArray)
{
result.Add(new Modulus(sm));
}
return(result);
}
/// <summary>
/// Returns the largest bit-length of the coefficient modulus, i.e., bit-length
/// of the product of the primes in the coefficient modulus, that guarantees
/// a given security level when using a given PolyModulusDegree, according
/// to the HomomorphicEncryption.org security standard.
/// </summary>
/// <param name="polyModulusDegree">The value of the PolyModulusDegree
/// encryption parameter</param>
/// <param name="secLevel">The desired standard security level</param>
static public int MaxBitCount(ulong polyModulusDegree, SecLevelType secLevel = SecLevelType.TC128)
{
NativeMethods.CoeffModulus_MaxBitCount(polyModulusDegree, (int)secLevel, out int result);
return(result);
}
