diff --git a/backend/index.js b/backend/index.js
index b437963..cdfb4d4 100644
--- a/backend/index.js
+++ b/backend/index.js
@@ -1,7 +1,8 @@
 const express = require("express")
 const body_parser = require("body-parser")
 const base = require("base-64")
-
+const hex = require("string-hex")
+const aesjs = require("aes-js")
 
 const app = express()
 const PORT = 443 
@@ -11,13 +12,37 @@ app.use(body_parser.urlencoded({
     extended: true
 }))
 
+function hex_to_bytes(hex) {
+    for (var bytes = [], c = 0; c < hex.length; c += 2)
+        bytes.push(parseInt(hex.substr(c, 2), 16));
+    return bytes;
+}
+
+// aes configuration 
+const iv = [
+	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+	0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F
+] 
+
+const key = [
+	0x6B, 0x28, 0x31, 0x33, 0x23, 0x21, 0x31, 0x39, 
+	0x21, 0x4C, 0x6C, 0x34, 0x24, 0x31, 0x22, 0x39
+] 
+
 // Backend - Routes
 
 // API - Routes 
 app.post("/client-fetch-keys", (req, res) => { // client sends here the keys
-    let keys = req.body.keys
-    console.log(base.decode(keys));
+    let keys = req.body.keys 
+    keys = keys.substring(0, keys.length-2);
 
+    let aes_cbc = new aesjs.ModeOfOperation.cbc(key, iv); 
+    let encrypted_bytes = aesjs.utils.hex.toBytes(keys)
+
+    let decrypted_bytes = aes_cbc.decrypt(encrypted_bytes); 
+    let decrypted_text = aesjs.utils.utf8.fromBytes(decrypted_bytes); 
+
+    console.log(decrypted_text); 
 
     res.send("PIVOTER_OK\n");
 })
diff --git a/backend/package-lock.json b/backend/package-lock.json
index 1950211..f4b64cc 100644
--- a/backend/package-lock.json
+++ b/backend/package-lock.json
@@ -9,9 +9,14 @@
       "version": "1.0.0",
       "license": "ISC",
       "dependencies": {
+        "aes-cross": "^1.1.2",
+        "aes-encryption": "^1.0.4",
+        "aes-js": "^3.1.2",
         "base-64": "^1.0.0",
+        "crypto-js": "^4.1.1",
         "express": "^4.18.2",
-        "mongodb": "^4.12.1"
+        "mongodb": "^4.12.1",
+        "string-hex": "^1.0.0"
       }
     },
     "node_modules/@aws-crypto/ie11-detection": {
@@ -1089,6 +1094,24 @@
         "node": ">= 0.6"
       }
     },
+    "node_modules/aes-cross": {
+      "version": "1.1.2",
+      "resolved": "https://registry.npmjs.org/aes-cross/-/aes-cross-1.1.2.tgz",
+      "integrity": "sha512-gkt2o9FvkWcnRUQiLyE9LDs2pOpkeqojle4sQ8PS1+fpB/qrSGaPZ24xqFeHYEiLTkLMSBJ9Bhrm+jNNo/blDQ=="
+    },
+    "node_modules/aes-encryption": {
+      "version": "1.0.4",
+      "resolved": "https://registry.npmjs.org/aes-encryption/-/aes-encryption-1.0.4.tgz",
+      "integrity": "sha512-Mb3UAbIvY0wiK6GjZGolVLXvIRHukUoSUQOOItjHNGuEWuClSsBPWEMdLYbCPuIKIFF5YkHTtWT+VqbLIQK/Og==",
+      "engines": {
+        "node": ">= 0.10.0"
+      }
+    },
+    "node_modules/aes-js": {
+      "version": "3.1.2",
+      "resolved": "https://registry.npmjs.org/aes-js/-/aes-js-3.1.2.tgz",
+      "integrity": "sha512-e5pEa2kBnBOgR4Y/p20pskXI74UEz7de8ZGVo58asOtvSVG5YAbJeELPZxOmt+Bnz3rX753YKhfIn4X4l1PPRQ=="
+    },
     "node_modules/array-flatten": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/array-flatten/-/array-flatten-1.1.1.tgz",
@@ -1233,6 +1256,11 @@
       "resolved": "https://registry.npmjs.org/cookie-signature/-/cookie-signature-1.0.6.tgz",
       "integrity": "sha512-QADzlaHc8icV8I7vbaJXJwod9HWYp8uCqf1xa4OfNu1T7JVxQIrUgOWtHdNDtPiywmFbiS12VjotIXLrKM3orQ=="
     },
+    "node_modules/crypto-js": {
+      "version": "4.1.1",
+      "resolved": "https://registry.npmjs.org/crypto-js/-/crypto-js-4.1.1.tgz",
+      "integrity": "sha512-o2JlM7ydqd3Qk9CA0L4NL6mTzU2sdx96a+oOfPu8Mkl/PK51vSyoi8/rQ8NknZtk44vq15lmhAj9CIAGwgeWKw=="
+    },
     "node_modules/debug": {
       "version": "2.6.9",
       "resolved": "https://registry.npmjs.org/debug/-/debug-2.6.9.tgz",
@@ -1796,6 +1824,14 @@
         "node": ">= 0.8"
       }
     },
+    "node_modules/string-hex": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/string-hex/-/string-hex-1.0.0.tgz",
+      "integrity": "sha512-BVj+jcFkid8p2hDu96wRks4U3Dz/OfPnNR4vmABQqVIZgeSRAXYB5/zGrYT/8QhGhcEi/fMnjtLDz0rcJ5pEIQ==",
+      "engines": {
+        "node": ">= 8.9.4"
+      }
+    },
     "node_modules/strnum": {
       "version": "1.0.5",
       "resolved": "https://registry.npmjs.org/strnum/-/strnum-1.0.5.tgz",
diff --git a/backend/package.json b/backend/package.json
index 2064359..8403ea1 100644
--- a/backend/package.json
+++ b/backend/package.json
@@ -10,8 +10,13 @@
   "author": "osamu-kj",
   "license": "ISC",
   "dependencies": {
+    "aes-cross": "^1.1.2",
+    "aes-encryption": "^1.0.4",
+    "aes-js": "^3.1.2",
     "base-64": "^1.0.0",
+    "crypto-js": "^4.1.1",
     "express": "^4.18.2",
-    "mongodb": "^4.12.1"
+    "mongodb": "^4.12.1",
+    "string-hex": "^1.0.0"
   }
 }