diff --git a/openid-zkp-auth/circuits/helpers/strings.circom b/openid-zkp-auth/circuits/helpers/strings.circom
index e064585169..b1d375e979 100644
--- a/openid-zkp-auth/circuits/helpers/strings.circom
+++ b/openid-zkp-auth/circuits/helpers/strings.circom
@@ -90,37 +90,6 @@ template Slice(inLen, outLen) {
     }
 }
 
-// in[index: index + length*groupLen] + [0] * (outLen - length)*groupLen
-// template SliceGrouped(inLen, outLen, groupLen) {
-//     signal input in[inLen];
-//     signal input index;
-//     signal input length;
-
-//     signal output out[outLen * groupLen];
-
-//     // eqs[i] = 1 if i = index, 0 otherwise
-//     signal eqs[inLen] <== OneBitVector(inLen)(index);
-//     // lt[i] = 1 if i < length, 0 otherwise
-//     signal lts[outLen] <== LTBitVector(outLen)(length);
-
-//     signal tmp[outLen];
-//     for(var i = 0; i < outLen; i++) {
-//         var arr[inLen];
-//         for (var j = 0; j < inLen; j++) {
-//             if (j < i) {
-//                 arr[j] = 0;
-//             } else {
-//                 arr[j] = eqs[j - i];
-//             }
-//         }
-//         tmp[i] <== EscalarProduct(inLen)(arr, in);
-
-//         for (var j = 0; j < groupLen; j++) {
-//             out[i * groupLen + j] <== tmp[i] * lts[i];
-//         }
-//     }
-// }
-
 /**
 Checks if an ASCII-encoded substring exists in a Base64-encoded string.
 
@@ -221,4 +190,51 @@ template ASCIISubstrExistsInB64(b64StrLen, maxA) {
         }
         MyForceEqualIfEnabled()(enabled_2[i \ 8], [A_in_bits[i], B_in_bits[i + 4]]);
     }
+}
+
+/**
+JSON value extractor. 
+
+Given a JSON member with string JSON values as input, 
+    parses it according to JSON grammar and returns the JSON value.
+
+" s u b " x x x x : x x " 1 2 3 4 5 " x x x x x , 0 0 0 0 0
+                  |     |           |           |
+                  i     j           k           l
+
+Check that 
+    - in[0..3] = "sub"
+    - in[3..i] = ws
+    - in[i] = '"'
+    - in[i+1..j] = ws
+    - in[j] = '"'
+    - in[k] = '"'
+    - in[k+1..l] = ws
+    - in[l] = ',' or '}'
+    - in[l+1..endIndex] = 0
+
+Where ws = " " | "\t" | "\n" | "\r" or 0x20 | 0x09 | 0x0A | 0x0D
+**/
+template JSONValueExtractor(maxMemberLen, maxValueLen) {
+    signal input in[maxMemberLen];
+    signal input colonIndex;
+    signal input startQuoteIndex;
+    signal input endQuoteIndex;
+    signal input endCharIndex;
+
+    signal output out[maxValueLen];
+
+    in[0] === 0x22; // '"'
+    in[1] === 0x73; // 's'
+    in[2] === 0x75; // 'u'
+    in[3] === 0x62; // 'b'
+    in[4] === 0x22; // '"'
+
+    signal startquote <== SingleMultiplexer(maxMemberLen)(in, startQuoteIndex);
+    startquote === 0x22; // '"'
+    signal endquote <== SingleMultiplexer(maxMemberLen)(in, endQuoteIndex);
+    endquote === 0x22; // '"'
+
+    signal lastchar <== SingleMultiplexer(maxMemberLen)(in, endCharIndex);
+    (lastchar - 0x2C) * (lastchar - 0x7D) === 0; // ',' or '}'
 }
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