diff --git a/src/core/operations/ECDSASign.mjs b/src/core/operations/ECDSASign.mjs
index 5cce8cc2..0278eeeb 100644
--- a/src/core/operations/ECDSASign.mjs
+++ b/src/core/operations/ECDSASign.mjs
@@ -48,7 +48,7 @@ class ECDSASign extends Operation {
                 value: [
                     "ASN.1 HEX",
                     "P1363 HEX",
-                    "JSON"
+                    "Raw JSON"
                 ]
             }
         ];
@@ -86,7 +86,7 @@ class ECDSASign extends Operation {
             case "P1363 HEX":
                 result = r.KJUR.crypto.ECDSA.asn1SigToConcatSig(signatureASN1Hex);
                 break;
-            case "JSON": {
+            case "Raw JSON": {
                 const signatureRS = r.KJUR.crypto.ECDSA.parseSigHexInHexRS(signatureASN1Hex);
                 result = JSON.stringify(signatureRS);
                 break;
diff --git a/src/core/operations/ECDSASignatureConversion.mjs b/src/core/operations/ECDSASignatureConversion.mjs
index 1dfcb4d1..49c5ef53 100644
--- a/src/core/operations/ECDSASignatureConversion.mjs
+++ b/src/core/operations/ECDSASignatureConversion.mjs
@@ -5,6 +5,7 @@
  */
 
 import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
 import r from "jsrsasign";
 
 /**
@@ -32,7 +33,7 @@ class ECDSASignatureConversion extends Operation {
                     "Auto",
                     "ASN.1 HEX",
                     "P1363 HEX",
-                    "JSON"
+                    "Raw JSON"
                 ]
             },
             {
@@ -41,7 +42,7 @@ class ECDSASignatureConversion extends Operation {
                 value: [
                     "ASN.1 HEX",
                     "P1363 HEX",
-                    "JSON"
+                    "Raw JSON"
                 ]
             }
         ];
@@ -57,11 +58,19 @@ class ECDSASignatureConversion extends Operation {
         const outputFormat = args[1];
 
         // detect input format
+        let inputJson;
         if (inputFormat === "Auto") {
-            if (input.substr(0, 2) === "30" && r.ASN1HEX.isASN1HEX(input)) {
+            try {
+                inputJson = JSON.parse(input);
+                if (typeof(inputJson) === "object") {
+                    inputFormat = "Raw JSON";
+                }
+            } catch {}
+        }
+
+        if (inputFormat === "Auto") {
+            if (input.substring(0, 2) === "30" && r.ASN1HEX.isASN1HEX(input)) {
                 inputFormat = "ASN.1 HEX";
-            } else if (input.indexOf("{") !== -1) {
-                inputFormat = "JSON";
             } else {
                 inputFormat = "P1363 HEX";
             }
@@ -76,8 +85,14 @@ class ECDSASignatureConversion extends Operation {
             case "P1363 HEX":
                 signatureASN1Hex = r.KJUR.crypto.ECDSA.concatSigToASN1Sig(input);
                 break;
-            case "JSON": {
-                const inputJson = JSON.parse(input);
+            case "Raw JSON": {
+                if (!inputJson) inputJson = JSON.parse(input);
+                if (!inputJson.r) {
+                    throw new OperationError('No "r" value in the signature JSON');
+                }
+                if (!inputJson.s) {
+                    throw new OperationError('No "s" value in the signature JSON');
+                }
                 signatureASN1Hex = r.KJUR.crypto.ECDSA.hexRSSigToASN1Sig(inputJson.r, inputJson.s);
                 break;
             }
@@ -92,7 +107,7 @@ class ECDSASignatureConversion extends Operation {
             case "P1363 HEX":
                 result = r.KJUR.crypto.ECDSA.asn1SigToConcatSig(signatureASN1Hex);
                 break;
-            case "JSON": {
+            case "Raw JSON": {
                 const signatureRS = r.KJUR.crypto.ECDSA.parseSigHexInHexRS(signatureASN1Hex);
                 result = JSON.stringify(signatureRS);
                 break;
diff --git a/src/core/operations/ECDSAVerify.mjs b/src/core/operations/ECDSAVerify.mjs
index 8f3174a2..2cd38398 100644
--- a/src/core/operations/ECDSAVerify.mjs
+++ b/src/core/operations/ECDSAVerify.mjs
@@ -33,7 +33,7 @@ class ECDSAVerify extends Operation {
                     "Auto",
                     "ASN.1 HEX",
                     "P1363 HEX",
-                    "JSON"
+                    "Raw JSON"
                 ]
             },
             {
@@ -74,11 +74,19 @@ class ECDSAVerify extends Operation {
         }
 
         // detect input format
+        let inputJson;
         if (inputFormat === "Auto") {
-            if (input.substr(0, 2) === "30" && r.ASN1HEX.isASN1HEX(input)) {
+            try {
+                inputJson = JSON.parse(input);
+                if (typeof(inputJson) === "object") {
+                    inputFormat = "Raw JSON";
+                }
+            } catch {}
+        }
+
+        if (inputFormat === "Auto") {
+            if (input.substring(0, 2) === "30" && r.ASN1HEX.isASN1HEX(input)) {
                 inputFormat = "ASN.1 HEX";
-            } else if (input.indexOf("{") !== -1) {
-                inputFormat = "JSON";
             } else {
                 inputFormat = "P1363 HEX";
             }
@@ -93,8 +101,14 @@ class ECDSAVerify extends Operation {
             case "P1363 HEX":
                 signatureASN1Hex = r.KJUR.crypto.ECDSA.concatSigToASN1Sig(input);
                 break;
-            case "JSON": {
-                const inputJson = JSON.parse(input);
+            case "Raw JSON": {
+                if (!inputJson) inputJson = JSON.parse(input);
+                if (!inputJson.r) {
+                    throw new OperationError('No "r" value in the signature JSON');
+                }
+                if (!inputJson.s) {
+                    throw new OperationError('No "s" value in the signature JSON');
+                }
                 signatureASN1Hex = r.KJUR.crypto.ECDSA.hexRSSigToASN1Sig(inputJson.r, inputJson.s);
                 break;
             }
diff --git a/tests/operations/tests/ECDSA.mjs b/tests/operations/tests/ECDSA.mjs
index 8fe93ef3..f0d4305a 100644
--- a/tests/operations/tests/ECDSA.mjs
+++ b/tests/operations/tests/ECDSA.mjs
@@ -271,6 +271,28 @@ TestRegister.addTests([
             }
         ]
     },
+    {
+        name: "ECDSA Verify: JSON signature missing r",
+        input: JSON.stringify({s: JSON.parse(P256.signature.sha256.json).s}),
+        expectedOutput: 'No "r" value in the signature JSON',
+        recipeConfig: [
+            {
+                "op": "ECDSA Verify",
+                "args": ["Auto", "SHA-256", P256.publicKey, ASCII_TEXT]
+            }
+        ]
+    },
+    {
+        name: "ECDSA Verify: JSON signature missing s",
+        input: JSON.stringify({r: JSON.parse(P256.signature.sha256.json).r}),
+        expectedOutput: 'No "s" value in the signature JSON',
+        recipeConfig: [
+            {
+                "op": "ECDSA Verify",
+                "args": ["Auto", "SHA-256", P256.publicKey, ASCII_TEXT]
+            }
+        ]
+    },
     {
         name: "ECDSA Verify: Using private key fails",
         input: P256.signature.sha256.asn1,
@@ -324,7 +346,7 @@ TestRegister.addTests([
         recipeConfig: [
             {
                 "op": "ECDSA Signature Conversion",
-                "args": ["Auto", "JSON"]
+                "args": ["Auto", "Raw JSON"]
             }
         ]
     },
@@ -357,7 +379,7 @@ TestRegister.addTests([
         recipeConfig: [
             {
                 "op": "ECDSA Signature Conversion",
-                "args": ["Auto", "JSON"]
+                "args": ["Auto", "Raw JSON"]
             }
         ]
     },
@@ -390,7 +412,7 @@ TestRegister.addTests([
         recipeConfig: [
             {
                 "op": "ECDSA Signature Conversion",
-                "args": ["Auto", "JSON"]
+                "args": ["Auto", "Raw JSON"]
             }
         ]
     }