[#3] Move to netstandard 2.0

Signed-off-by: Pavel Gross <p.gross@yadro.com>

src/FrostFS.SDK.Cryptography/Key.cs

@@ -1,7 +1,10 @@
-using System.Buffers.Binary;
+using System;
+using System.Buffers.Binary;
+using System.Linq;
 using System.Numerics;
 using System.Security.Cryptography;
 using System.Text;
+
 using Org.BouncyCastle.Asn1.Sec;
 
 namespace FrostFS.SDK.Cryptography;
@@ -22,8 +25,10 @@ public static class KeyExtension
                 $"{nameof(Compress)} argument isn't uncompressed public key. " +
                 $"expected length={UncompressedPublicKeyLength}, actual={publicKey.Length}"
             );
+
         var secp256R1 = SecNamedCurves.GetByName("secp256r1");
         var point = secp256R1.Curve.DecodePoint(publicKey);
+
         return point.GetEncoded(true);
     }
 
@@ -34,8 +39,10 @@ public static class KeyExtension
                 $"{nameof(Decompress)} argument isn't compressed public key. " +
                 $"expected length={CompressedPublicKeyLength}, actual={publicKey.Length}"
             );
+
         var secp256R1 = SecNamedCurves.GetByName("secp256r1");
         var point = secp256R1.Curve.DecodePoint(publicKey);
+
         return point.GetEncoded(false);
     }
 
@@ -46,10 +53,12 @@ public static class KeyExtension
                 $"{nameof(CreateSignatureRedeemScript)} argument isn't compressed public key. " +
                 $"expected length={CompressedPublicKeyLength}, actual={publicKey.Length}"
             );
+
         var script = new byte[] { 0x0c, CompressedPublicKeyLength }; //PUSHDATA1 33
         script = ArrayHelper.Concat(script, publicKey);
         script = ArrayHelper.Concat(script, new byte[] { 0x41 }); //SYSCALL
         script = ArrayHelper.Concat(script, BitConverter.GetBytes(CheckSigDescriptor)); //Neo_Crypto_CheckSig
+
         return script;
     }
 
@@ -64,15 +73,20 @@ public static class KeyExtension
         Span<byte> data = stackalloc byte[21];
         data[0] = version;
         scriptHash.CopyTo(data[1..]);
+
         return Base58.Base58CheckEncode(data);
     }
 
     private static byte[] GetPrivateKeyFromWIF(string wif)
     {
-        if (wif == null) throw new ArgumentNullException();
+        if (wif == null) 
+            throw new ArgumentNullException();
+        
         var data = wif.Base58CheckDecode();
+        
         if (data.Length != 34 || data[0] != 0x80 || data[33] != 0x01)
             throw new FormatException();
+      
         var privateKey = new byte[32];
         Buffer.BlockCopy(data, 1, privateKey, 0, privateKey.Length);
         Array.Clear(data, 0, data.Length);
@@ -92,6 +106,7 @@ public static class KeyExtension
                 $" isn't encoded compressed public key. " +
                 $"expected length={CompressedPublicKeyLength}, actual={publicKey.Length}"
             );
+
         return publicKey.GetScriptHash().ToAddress(NeoAddressVersion);
     }
 
@@ -130,12 +145,14 @@ public static class KeyExtension
                 Y = publicKey[32..]
             }
         });
+
         return key;
     }
 
     public static ECDsa LoadWif(this string wif)
     {
         var privateKey = GetPrivateKeyFromWIF(wif);
+        
         return LoadPrivateKey(privateKey);
     }
 
@@ -151,6 +168,7 @@ public static class KeyExtension
                 Y = publicKeyFull[32..]
             }
         });
+
         return key;
     }
 }