(.NET Core C#) Validate a JWS Using ECDSA P-256 SHA-256

Validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256

Note: This example requires Chilkat v9.5.0.66 or greater.

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// This requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// Note: This example requires Chilkat v9.5.0.66 or greater.

// This example takes a JSON signature in compact serialization format,
// and uses an ECDSA public key to validate and recover the protected header and payload.

// We only need a public key for signature validation.  This is the ECDSA public key
// that is used:

//      {"kty":"EC", 
//       "crv":"P-256", 
//       "x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU", 
//       "y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0" 
//      } 

Chilkat.StringBuilder sbPubKey = new Chilkat.StringBuilder();
sbPubKey.Append("{\"kty\":\"EC\",");
sbPubKey.Append("\"crv\":\"P-256\",");
sbPubKey.Append("\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\",");
sbPubKey.Append("\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\"");
sbPubKey.Append("}");

Chilkat.PublicKey pubKey = new Chilkat.PublicKey();
bool success = pubKey.LoadFromString(sbPubKey.GetAsString());
if (success != true) {
    Debug.WriteLine(pubKey.LastErrorText);
    return;
}

Chilkat.Jws jws = new Chilkat.Jws();

// Set the ECC public key:
int signatureIndex = 0;
jws.SetPublicKey(signatureIndex,pubKey);

// Load the JWS.
Chilkat.StringBuilder sbJws = new Chilkat.StringBuilder();
sbJws.Append("eyJhbGciOiJFUzI1NiJ9");
sbJws.Append(".");
sbJws.Append("eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt");
sbJws.Append("cGxlLmNvbS9pc19yb290Ijp0cnVlfQ");
sbJws.Append(".");
sbJws.Append("DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA");
sbJws.Append("pmWQxfKTUJqPP3-Kg6NU1Q");

success = jws.LoadJwsSb(sbJws);
if (success != true) {
    Debug.WriteLine(jws.LastErrorText);
    return;
}

// Validate the 1st (and only) signature at index 0..
int v = jws.Validate(signatureIndex);
if (v < 0) {
    // Perhaps Chilkat was not unlocked or the trial expired..
    Debug.WriteLine("Method call failed for some other reason.");
    Debug.WriteLine(jws.LastErrorText);
    return;
}

if (v == 0) {
    Debug.WriteLine("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.");
    return;
}

// If we get here, the signature was validated..
Debug.WriteLine("Signature validated.");
Debug.WriteLine("--");

// Recover the original content:
Debug.WriteLine("Recovered content:");
Debug.WriteLine(jws.GetPayload("utf-8"));
Debug.WriteLine("--");

// Examine the protected header:
Chilkat.JsonObject joseHeader = jws.GetProtectedHeader(signatureIndex);
if (jws.LastMethodSuccess != true) {
    Debug.WriteLine("No protected header found at the given index.");
    return;
}

joseHeader.EmitCompact = false;

Debug.WriteLine("Protected (JOSE) header:");
Debug.WriteLine(joseHeader.Emit());

// Output:

// 	Signature validated.
// 	--
// 	Recovered content:
// 	{"iss":"joe",
// 	 "exp":1300819380,
// 	 "http://example.com/is_root":true}
// 	--
// 	Protected (JOSE) header:
// 	{ 
// 	  "alg": "ES256"
// 	}