internal static bool Pubkey_parse(ReadOnlySpan <byte> pub, out bool compressed, out GE elem)
{
compressed = false;
elem = default;
if (pub.Length == 33 && (pub[0] == SECP256K1_TAG_PUBKEY_EVEN || pub[0] == SECP256K1_TAG_PUBKEY_ODD))
{
compressed = true;
return
(FE.TryCreate(pub.Slice(1), out var x) &&
GE.TryCreateXOVariable(x, pub[0] == SECP256K1_TAG_PUBKEY_ODD, out elem));
}
else if (pub.Length == 65 && (pub[0] == SECP256K1_TAG_PUBKEY_UNCOMPRESSED || pub[0] == SECP256K1_TAG_PUBKEY_HYBRID_EVEN || pub[0] == SECP256K1_TAG_PUBKEY_HYBRID_ODD))
{
if (!FE.TryCreate(pub.Slice(1), out var x) || !FE.TryCreate(pub.Slice(33), out var y))
{
return(false);
}
elem = new GE(x, y);
if ((pub[0] == SECP256K1_TAG_PUBKEY_HYBRID_EVEN || pub[0] == SECP256K1_TAG_PUBKEY_HYBRID_ODD) &&
y.IsOdd != (pub[0] == SECP256K1_TAG_PUBKEY_HYBRID_ODD))
{
return(false);
}
return(elem.IsValidVariable);
}
else
{
return(false);
}
}
public ECMultGenContext()
{
Span <GE> prec = stackalloc GE[1024];
GEJ gj;
GEJ nums_gej;
int i, j;
this.prec = new GEStorage[64, 16];
gj = EC.G.ToGroupElementJacobian();
/* Construct a group element with no known corresponding scalar (nothing up my sleeve). */
{
var nums_b32 = "The scalar for this x is unknown".ToCharArray().Select(b => (byte)b).ToArray();
FE nums_x;
GE nums_ge;
var r = FE.TryCreate(nums_b32, out nums_x);
VERIFY_CHECK(r);
r = GE.TryCreateXOVariable(nums_x, false, out nums_ge);
VERIFY_CHECK(r);
nums_gej = nums_ge.ToGroupElementJacobian();
/* Add G to make the bits in x uniformly distributed. */
nums_gej = nums_gej.AddVariable(EC.G, out _);
}
/* compute prec. */
{
Span <GEJ> precj = stackalloc GEJ[1024]; /* Jacobian versions of prec. */
GEJ gbase;
GEJ numsbase;
gbase = gj; /* 16^j * G */
numsbase = nums_gej; /* 2^j * nums. */
for (j = 0; j < 64; j++)
{
/* Set precj[j*16 .. j*16+15] to (numsbase, numsbase + gbase, ..., numsbase + 15*gbase). */
precj[j * 16] = numsbase;
for (i = 1; i < 16; i++)
{
precj[j * 16 + i] = precj[j * 16 + i - 1].AddVariable(gbase, out _);
}
/* Multiply gbase by 16. */
for (i = 0; i < 4; i++)
{
gbase = gbase.DoubleVariable();
}
/* Multiply numbase by 2. */
numsbase = numsbase.DoubleVariable();
if (j == 62)
{
/* In the last iteration, numsbase is (1 - 2^j) * nums instead. */
numsbase = numsbase.Negate();
numsbase = numsbase.AddVariable(nums_gej, out _);
}
}
GE.SetAllGroupElementJacobianVariable(prec, precj, 1024);
}
for (j = 0; j < 64; j++)
{
for (i = 0; i < 16; i++)
{
this.prec[j, i] = prec[j * 16 + i].ToStorage();
}
}
Blind();
}
