diff --git a/crypto/src/math/ec/rfc7748/X25519.cs b/crypto/src/math/ec/rfc7748/X25519.cs
index 16f680d90..8c52a21ac 100644
--- a/crypto/src/math/ec/rfc7748/X25519.cs
+++ b/crypto/src/math/ec/rfc7748/X25519.cs
@@ -54,63 +54,68 @@ namespace Org.BouncyCastle.Math.EC.Rfc7748
X25519Field.Mul(z, A, z);
}
- [MethodImpl(MethodImplOptions.Synchronized)]
+ // https://stackoverflow.com/questions/2223656/what-does-methodimploptions-synchronized-do
+ // Not available in lower .net standard versions
+ //[MethodImpl(MethodImplOptions.Synchronized)]
public static void Precompute()
{
- if (precompBase != null)
- return;
+ lock (typeof(X25519))
+ {
+ if (precompBase != null)
+ return;
- precompBase = new int[X25519Field.Size * 252];
+ precompBase = new int[X25519Field.Size * 252];
- int[] xs = precompBase;
- int[] zs = new int[X25519Field.Size * 251];
+ int[] xs = precompBase;
+ int[] zs = new int[X25519Field.Size * 251];
- int[] x = X25519Field.Create(); x[0] = 9;
- int[] z = X25519Field.Create(); z[0] = 1;
+ int[] x = X25519Field.Create(); x[0] = 9;
+ int[] z = X25519Field.Create(); z[0] = 1;
- int[] n = X25519Field.Create();
- int[] d = X25519Field.Create();
+ int[] n = X25519Field.Create();
+ int[] d = X25519Field.Create();
- X25519Field.Apm(x, z, n, d);
+ X25519Field.Apm(x, z, n, d);
- int[] c = X25519Field.Create(); X25519Field.Copy(d, 0, c, 0);
+ int[] c = X25519Field.Create(); X25519Field.Copy(d, 0, c, 0);
- int off = 0;
- for (;;)
- {
- X25519Field.Copy(n, 0, xs, off);
+ int off = 0;
+ for (; ; )
+ {
+ X25519Field.Copy(n, 0, xs, off);
- if (off == (X25519Field.Size * 251))
- break;
+ if (off == (X25519Field.Size * 251))
+ break;
- PointDouble(x, z);
+ PointDouble(x, z);
- X25519Field.Apm(x, z, n, d);
- X25519Field.Mul(n, c, n);
- X25519Field.Mul(c, d, c);
+ X25519Field.Apm(x, z, n, d);
+ X25519Field.Mul(n, c, n);
+ X25519Field.Mul(c, d, c);
- X25519Field.Copy(d, 0, zs, off);
+ X25519Field.Copy(d, 0, zs, off);
- off += X25519Field.Size;
- }
+ off += X25519Field.Size;
+ }
- int[] u = X25519Field.Create();
- X25519Field.Inv(c, u);
+ int[] u = X25519Field.Create();
+ X25519Field.Inv(c, u);
- for (;;)
- {
- X25519Field.Copy(xs, off, x, 0);
+ for (; ; )
+ {
+ X25519Field.Copy(xs, off, x, 0);
- X25519Field.Mul(x, u, x);
- //X25519Field.Normalize(x);
- X25519Field.Copy(x, 0, precompBase, off);
+ X25519Field.Mul(x, u, x);
+ //X25519Field.Normalize(x);
+ X25519Field.Copy(x, 0, precompBase, off);
- if (off == 0)
- break;
+ if (off == 0)
+ break;
- off -= X25519Field.Size;
- X25519Field.Copy(zs, off, z, 0);
- X25519Field.Mul(u, z, u);
+ off -= X25519Field.Size;
+ X25519Field.Copy(zs, off, z, 0);
+ X25519Field.Mul(u, z, u);
+ }
}
}
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