diff --git a/backend/models/community/user.js b/backend/models/community/user.js
index ecde458..99eeb2e 100644
--- a/backend/models/community/user.js
+++ b/backend/models/community/user.js
@@ -1,6 +1,7 @@
 import { sequelize } from '../../utils/sequelize.js';
 import { DataTypes } from 'sequelize';
 import bcrypt from 'bcrypt';
+import { encrypt, generateIv } from '../../utils/encryption.js';
 
 const User = sequelize.define('user', {
     email: {
@@ -8,9 +9,17 @@ const User = sequelize.define('user', {
         allowNull: false,
         unique: true,
         set(value) {
-            this.setDataValue('email', bcrypt.hashSync(value, 10));
+            if (value) {
+                const iv = generateIv();
+                this.setDataValue('iv', iv.toString('hex'));
+                this.setDataValue('email', encrypt(value, iv));
+            }
         }
     },
+    iv: {
+        type: DataTypes.STRING,
+        allowNull: false
+    },
     username: {
         type: DataTypes.STRING,
         allowNull: false,
@@ -19,6 +28,9 @@ const User = sequelize.define('user', {
     password: {
         type: DataTypes.STRING,
         allowNull: false,
+        set(value) {
+            this.setDataValue('password', bcrypt.hashSync(value, 10));
+        }
     },
     registrationDate: {
         type: DataTypes.DATE,
@@ -29,7 +41,7 @@ const User = sequelize.define('user', {
         type: DataTypes.BOOLEAN,
         defaultValue: false
     },
-    resetToken: {
+    resetToken: { 
         type: DataTypes.UUID,
         allowNull: true
     },
@@ -40,7 +52,7 @@ const User = sequelize.define('user', {
 }, {
     tableName: 'user',
     schema: 'community',
-    underscored: true,
+    underscored: true
 });
 
 export default User;
diff --git a/backend/models/community/user_param.js b/backend/models/community/user_param.js
index c75c0b9..01340fd 100644
--- a/backend/models/community/user_param.js
+++ b/backend/models/community/user_param.js
@@ -2,6 +2,7 @@ import { sequelize } from '../../utils/sequelize.js';
 import { DataTypes } from 'sequelize';
 import User from './user.js';
 import UserParamType from '../type/user_param.js';
+import { encrypt, decrypt, generateIv } from '../../utils/encryption.js';
 
 const UserParam = sequelize.define('user_param', {
     userId: {
@@ -18,20 +19,52 @@ const UserParam = sequelize.define('user_param', {
         references: {
             model: UserParamType,
             key: 'id'
-        },
-        
+        }
     },
     value: {
+        type: DataTypes.STRING,
+        allowNull: false,
+        set(value) {
+            if (value) {
+                const iv = generateIv();
+                this.setDataValue('iv', iv.toString('hex'));
+                this.setDataValue('value', encrypt(value, iv));
+            }
+        }
+    },
+    iv: {
         type: DataTypes.STRING,
         allowNull: false
     }
 }, {
     tableName: 'user_param',
     schema: 'community',
-    underscored: true
+    underscored: true,
+    hooks: {
+        beforeSave: (userParam) => {
+            if (userParam.value && !userParam.iv) {
+                const iv = generateIv();
+                userParam.iv = iv.toString('hex');
+                userParam.value = encrypt(userParam.value, iv);
+            }
+        },
+        afterFind: (userParams) => {
+            if (userParams) {
+                if (Array.isArray(userParams)) {
+                    userParams.forEach((userParam) => {
+                        const iv = Buffer.from(userParam.iv, 'hex');
+                        userParam.value = decrypt(userParam.value, iv);
+                    });
+                } else {
+                    const iv = Buffer.from(userParams.iv, 'hex');
+                    userParams.value = decrypt(userParams.value, iv);
+                }
+            }
+        }
+    }
 });
 
 UserParam.belongsTo(User, { foreignKey: 'userId' });
-UserParam.belongsTo(UserParamType, { foreignKey: 'param_type_id' });
+UserParam.belongsTo(UserParamType, { foreignKey: 'paramTypeId' });
 
 export default UserParam;
diff --git a/backend/services/authService.js b/backend/services/authService.js
index 0d0937b..2aee158 100644
--- a/backend/services/authService.js
+++ b/backend/services/authService.js
@@ -8,31 +8,40 @@ import { sendAccountActivationEmail, sendPasswordResetEmail } from './emailServi
 const saltRounds = 10;
 
 export const registerUser = async ({ email, username, password, language }) => {
+    const [results] = await sequelize.query(
+        'SELECT * FROM "community"."user" WHERE pgp_sym_decrypt("email", :key) = :email',
+        {
+            replacements: { key: process.env.SECRET_KEY, email },
+            type: sequelize.QueryTypes.SELECT
+        }
+    );
+    if (results.length > 0) {
+        throw new Error('Email already in use');
+    }
+    const iv = generateIv();
+    const encryptedEmail = encrypt(email, iv);
     const hashedPassword = await bcrypt.hash(password, saltRounds);
     const resetToken = uuidv4();
     const user = await User.create({
-        email,
+        email: encryptedEmail,
+        iv: iv.toString('hex'),
         username,
         password: hashedPassword,
         resetToken: resetToken,
         active: false,
         registration_date: new Date()
     });
-
     const languageType = await UserParamType.findOne({ where: { description: 'language' } });
     if (!languageType) {
         throw new Error('Language type not found');
     }
-
     await UserParam.create({
         userId: user.id,
         paramTypeId: languageType.id,
         value: language
     });
-
     const activationLink = `${process.env.FRONTEND_URL}/activate?token=${resetToken}`;
     await sendAccountActivationEmail(email, activationLink, username, resetToken, language);
-
     return { id: user.hashedId, username: user.username, active: user.active };
 };
 
diff --git a/backend/utils/encryption.js b/backend/utils/encryption.js
new file mode 100644
index 0000000..2f4f17f
--- /dev/null
+++ b/backend/utils/encryption.js
@@ -0,0 +1,32 @@
+import crypto from 'crypto';
+import dotenv from 'dotenv';
+
+dotenv.config(); // Laden der Umgebungsvariablen
+
+const algorithm = 'aes-256-cbc';
+const secretKey = process.env.SECRET_KEY;
+
+if (!secretKey || secretKey.length !== 32) {
+    throw new Error('SECRET_KEY length must be 32 bytes');
+}
+
+const encrypt = (text, iv) => {
+    const cipher = crypto.createCipheriv(algorithm, Buffer.from(secretKey, 'utf-8'), iv);
+    let encrypted = cipher.update(text);
+    encrypted = Buffer.concat([encrypted, cipher.final()]);
+    return encrypted.toString('hex');
+};
+
+const decrypt = (encryptedText, iv) => {
+    const encryptedBuffer = Buffer.from(encryptedText, 'hex');
+    const decipher = crypto.createDecipheriv(algorithm, Buffer.from(secretKey, 'utf-8'), iv);
+    let decrypted = decipher.update(encryptedBuffer);
+    decrypted = Buffer.concat([decrypted, decipher.final()]);
+    return decrypted.toString();
+};
+
+const generateIv = () => {
+    return crypto.randomBytes(16);
+};
+
+export { encrypt, decrypt, generateIv };