misc: add comments, clarify return type

Author: DennisDyallo

Yubico.YubiKey/src/Yubico/YubiKey/Cryptography/AsnPrivateKeyDecoder.cs

@@ -70,7 +70,7 @@ public static IPrivateKey CreatePrivateKey(ReadOnlyMemory<byte> pkcs8EncodedKey)
     public static Curve25519PrivateKey CreateCurve25519Key(ReadOnlyMemory<byte> pkcs8EncodedKey) =>
         Curve25519PrivateKey.CreateFromPkcs8(pkcs8EncodedKey);
 
-    public static (byte[], KeyType) GetCurve25519PrivateKeyData(ReadOnlyMemory<byte> pkcs8EncodedKey)
+    public static (byte[] privateKey, KeyType keyType) GetCurve25519PrivateKeyData(ReadOnlyMemory<byte> pkcs8EncodedKey)
     {
         var reader = new AsnReader(pkcs8EncodedKey, AsnEncodingRules.DER);
         var seqPrivateKeyInfo = reader.ReadSequence();

Yubico.YubiKey/src/Yubico/YubiKey/Cryptography/AsnUtilities.cs

@@ -84,9 +84,9 @@ public static Span<byte> GetIntegerBytes(Span<byte> value)
     /// <exception cref="CryptographicException">If the private key does not meet the bit clamping requirements.</exception>
     public static void VerifyX25519PrivateKey(ReadOnlySpan<byte> x25519PrivateKey)
     {
-        if ((x25519PrivateKey[0] & 0b111) != 0 || // Check that the 3 least significant bits are 0
-            (x25519PrivateKey[31] & 0x80) != 0 || // Check most significant bit is 0
-            (x25519PrivateKey[31] & 0x40) != 0x40) // Check second-most significant bit is 1
+        if ((x25519PrivateKey[0] & 0b111) != 0 || // Check that the 3 least significant bits are set
+            (x25519PrivateKey[31] & 0x80) != 0 || // Check most significant bit is set
+            (x25519PrivateKey[31] & 0x40) != 0x40) // Check second most significant bit not set
         {
             throw new CryptographicException("Invalid X25519 private key: improper bit clamping");
         }

Yubico.YubiKey/src/Yubico/YubiKey/Cryptography/Curve25519PrivateKey.cs

@@ -68,8 +68,6 @@ public override byte[] ExportPkcs8PrivateKey()
     /// </remarks>
     public override void Clear() => CryptographicOperations.ZeroMemory(_privateKey.Span);
 
-
-
     /// <summary>
     /// Creates an instance of <see cref="Curve25519PrivateKey"/> from a PKCS#8
     /// DER-encoded private key.

Yubico.YubiKey/tests/unit/Yubico/YubiKey/Cryptography/ZeroingMemoryHandleTests.cs

@@ -23,7 +23,6 @@ public class ZeroingMemoryHandleTests
     public void Dispose_ShouldClearArrayContent()
     {
         byte[] privateKeyData = new byte[] { 10, 20, 30, 40, 50 };
-
         using (var secureData = new ZeroingMemoryHandle(privateKeyData))
         {
             Assert.Equal(new byte[] { 10, 20, 30, 40, 50 }, secureData.Data);