lol

// ---------------------------------------------------------------------------------------
// Big Number Representations
//
// Multiple precision numbers are arranged as an array of digits, with the least
// significant digit coming first ("little-endian digit ordering"), regardless
// of the word size or byte ordering of the digit itself.
//
// A single digit is either a DWORD (4 bytes) or a QWORD (8 bytes).  A bignum that
// consists of a series of DWORD digits is tagged "BnDw", whereas a bignum that
// consists of a series of QWORD digits is tagged "BnQw".  A bignum function
// is tagged with one of these two to specify the digit size it expects, and it
// takes a length parameter that specifies the number of digits in the number.
//
// Consider a 8-byte number written in radix 256 notation.  Here R=256.
//
//     b7*(R^7)+b6*(R^6)+b5*(R^5)+b4*(R^5)+b3*(R^3)+b2*(R^2)+b1*(R^1)+b0*(R^0)
//
// A BnDw bignum consists of a series of DWORD digits.  The DWORD can be encoded
// in either little-endian or big-endian byte ordering.  Thus there are two
// possible formats for these digits.
//
//     DwLe     [b0 b1 b2 b3][b4 b5 b6 b7]
//     DwBe     [b3 b2 b1 b0][b7 b6 b5 b4]
//
// A BnQw bignum consists of a series of QWORD digits.  The QWORD can be encoded
// in either little-endian or big-endian byte ordering.  Thus there are two
// possible formats for these digits.
//
//     QwLe     [b0 b1 b2 b3 b4 b5 b6 b7]
//     QwBe     [b7 b6 b5 b4 b3 b2 b1 b0]
//
// A particular platform has a natural byte order (Le or Be).  We use the tag Ne
// to mean the natural byte order.
//
// Most low level bignum routines require inputs that are in QwNe format.  That
// is, QWORD digits in natural byte order for the platform.  They take an array
// of QWORD digits and a count of digits.  The caller is responsible for converting
// the bignum into the expected format.
//
// A full complement of conversion functions is available.  The BnDw functions
// will convert a bignum made up of a series of DWORD digits between DwLe, DwBe,
// and DwNe formats.  The BnQw functions will convert a bignum made up of a series
// of QWORD digits between QwLe, QwBe, and QwNe formats.  The BnQw functions can
// also convert between BnDw and BnQw bignum formats, but since the length parameter
// specifies the number of QWORD digits, the BnDw bignum must contain an even number
// of DWORD digits.
//
// When a bignum is to be stored or used on multiple platforms, the application
// must choose a concrete representation for the number.  In the case of digital
// signatures, we choose to store them in QwBe format.  This was chosen to match
// the natural word size and byte ordering of the Xenon console, so that the
// signature checking code would be as small and fast as possible on that platform.
// ---------------------------------------------------------------------------------------