/// <summary> /// Converts the given element in representation according to this field to a new element in /// representation according to B1 using the change-of-basis matrix calculated by computeCOBMatrix. /// </summary> /// /// <param name="Elem">The GF2nElement to convert</param> /// <param name="Basis">The basis to convert <c>Elem</c> to</param> /// /// <returns>Returns <c>Elem</c> converted to a new element representation according to <c>basis</c></returns> public GF2nElement Convert(GF2nElement Elem, GF2nField Basis) { if (Basis == this) return (GF2nElement)Elem.Clone(); if (FieldPoly.Equals(Basis.FieldPoly)) return (GF2nElement)Elem.Clone(); if (DegreeN != Basis.DegreeN) throw new Exception("GF2nField.Convert: B1 has a different degree and thus cannot be coverted to!"); int i; GF2Polynomial[] COBMatrix; i = Fields.IndexOf(Basis); if (i == -1) { ComputeCOBMatrix(Basis); i = Fields.IndexOf(Basis); } COBMatrix = (GF2Polynomial[])Matrices[i]; GF2nElement elemCopy = (GF2nElement)Elem.Clone(); if (elemCopy is GF2nONBElement) ((GF2nONBElement)elemCopy).ReverseOrder(); GF2Polynomial bs = new GF2Polynomial(DegreeN, elemCopy.ToFlexiBigInt()); bs.ExpandN(DegreeN); GF2Polynomial result = new GF2Polynomial(DegreeN); for (i = 0; i < DegreeN; i++) { if (bs.VectorMult(COBMatrix[i])) result.SetBit(DegreeN - 1 - i); } if (Basis is GF2nPolynomialField) { return new GF2nPolynomialElement((GF2nPolynomialField)Basis, result); } else if (Basis is GF2nONBField) { GF2nONBElement res = new GF2nONBElement((GF2nONBField)Basis, result.ToFlexiBigInt()); res.ReverseOrder(); return res; } else { throw new Exception("GF2nField.convert: B1 must be an instance of GF2nPolynomialField or GF2nONBField!"); } }