diff --git a/package.json b/package.json
index 801c7888..e1e4def1 100644
--- a/package.json
+++ b/package.json
@@ -47,7 +47,6 @@
     "bn.js": "^5.2.1",
     "buffer": "^6.0.3",
     "daisyui": "^4.11.1",
-    "ethers": "^6.13.4",
     "framer-motion": "^11.2.14",
     "postcss": "^8.4.38",
     "preact": "^10.12.1",
@@ -57,7 +56,6 @@
     "react-hook-form": "^7.51.5",
     "react-router-dom": "^6.8.1",
     "react-toastify": "^10.0.6",
-    "siwe": "^2.3.2",
     "stellar-base": "^11.0.1",
     "stellar-sdk": "^11.3.0",
     "tailwind": "^4.0.0",
@@ -80,7 +78,7 @@
     "@preact/preset-vite": "^2.9.1",
     "@types/big.js": "^6",
     "@types/bn.js": "^5",
-    "@types/node": "^18.14.1",
+    "@types/node": "^22.7.5",
     "@types/react": "^18.3.10",
     "@typescript-eslint/eslint-plugin": "^5.53.0",
     "@typescript-eslint/parser": "^5.53.0",
diff --git a/signer-service/src/api/controllers/siwe.controller.js b/signer-service/src/api/controllers/siwe.controller.js
index b07ddd62..ae43ff9f 100644
--- a/signer-service/src/api/controllers/siwe.controller.js
+++ b/signer-service/src/api/controllers/siwe.controller.js
@@ -17,14 +17,14 @@ exports.sendSiweMessage = async (req, res) => {
 exports.validateSiweSignature = async (req, res) => {
   const { nonce, signature, siweMessage } = req.body;
   try {
-    await verifyAndStoreSiweMessage(nonce, signature, siweMessage);
+    const address = await verifyAndStoreSiweMessage(nonce, signature, siweMessage);
 
     const token = {
       nonce,
       signature,
     };
 
-    res.cookie('authToken', token, {
+    res.cookie(`authToken_${address}`, token, {
       httpOnly: true,
       secure: true,
       sameSite: 'Strict',
diff --git a/signer-service/src/api/controllers/stellar.controller.js b/signer-service/src/api/controllers/stellar.controller.js
index b3c299d2..cbf29b4e 100644
--- a/signer-service/src/api/controllers/stellar.controller.js
+++ b/signer-service/src/api/controllers/stellar.controller.js
@@ -56,36 +56,14 @@ exports.changeOpTransaction = async (req, res, next) => {
 
 exports.signSep10Challenge = async (req, res, next) => {
   try {
-    let maybeChallengeSignature;
-    let maybeNonce;
-    if (req.cookies?.authToken) {
-      maybeChallengeSignature = req.cookies.authToken.signature;
-      maybeNonce = req.cookies.authToken.nonce;
-    }
-
-    if (Boolean(req.body.memo) && (!maybeChallengeSignature || !maybeNonce)) {
-      return res.status(401).json({
-        error: 'Missing signature or nonce',
-      });
-    }
-
     let { masterClientSignature, masterClientPublic, clientSignature, clientPublic } = await signSep10Challenge(
       req.body.challengeXDR,
       req.body.outToken,
       req.body.clientPublicKey,
-      maybeChallengeSignature,
-      maybeNonce,
+      req.derivedMemo, // Derived in middleware
     );
     return res.json({ masterClientSignature, masterClientPublic, clientSignature, clientPublic });
   } catch (error) {
-    if (error.message.includes('Could not verify signature')) {
-      // Distinguish between failed signature check and other errors.
-      return res.status(401).json({
-        error: 'Signature validation failed.',
-        details: error.message,
-      });
-    }
-
     console.error('Error in signSep10Challenge:', error);
     return res.status(500).json({ error: 'Failed to sign challenge', details: error.message });
   }
diff --git a/signer-service/src/api/helpers/memoDerivation.js b/signer-service/src/api/helpers/memoDerivation.js
new file mode 100644
index 00000000..59f9292f
--- /dev/null
+++ b/signer-service/src/api/helpers/memoDerivation.js
@@ -0,0 +1,21 @@
+const { keccak256 } = require('viem/utils');
+const { Keyring } = require('@polkadot/api');
+
+// Returns the hash value for the address. If it's a polkadot address, it will return raw data of the address.
+function getHashValueForAddress(address) {
+  if (address.startsWith('0x')) {
+    return address;
+  } else {
+    const keyring = new Keyring({ type: 'sr25519' });
+    return keyring.decodeAddress(address);
+  }
+}
+
+//A memo derivation.
+async function deriveMemoFromAddress(address) {
+  const hashValue = getHashValueForAddress(address);
+  const hash = keccak256(hashValue);
+  return BigInt(hash).toString().slice(0, 15);
+}
+
+module.exports = { deriveMemoFromAddress };
diff --git a/signer-service/src/api/helpers/siweMessageFormatter.js b/signer-service/src/api/helpers/siweMessageFormatter.js
new file mode 100644
index 00000000..86ca8804
--- /dev/null
+++ b/signer-service/src/api/helpers/siweMessageFormatter.js
@@ -0,0 +1,53 @@
+class SignInMessage {
+  // fixed statement string
+  static LOGIN_MESSAGE = ' wants you to sign in with your account: ';
+
+  constructor(fields) {
+    this.scheme = fields.scheme;
+    this.domain = fields.domain;
+    this.address = fields.address;
+    this.nonce = fields.nonce;
+    this.expirationTime = new Date(fields.expirationTime).toISOString();
+    this.issuedAt = fields.issuedAt ? new Date(fields.issuedAt).toISOString() : new Date().toISOString();
+  }
+
+  toMessage() {
+    const header = `${this.domain}${SignInMessage.LOGIN_MESSAGE}${this.address}`;
+
+    const body = `\nNonce: ${this.nonce}\nIssued At: ${this.issuedAt}\nExpiration Time: ${this.expirationTime}`;
+
+    return `${header}\n\n${body}`;
+  }
+
+  static fromMessage(message) {
+    const lines = message
+      .split('\n')
+      .map((l) => l.trim())
+      .filter((l) => l.length > 0);
+
+    const headerLine = lines.find((line) => line.includes(SignInMessage.LOGIN_MESSAGE)) || '';
+    const [domain, address] = headerLine.split(SignInMessage.LOGIN_MESSAGE).map((part) => part.trim());
+
+    const nonceLine = lines.find((line) => line.startsWith('Nonce:')) || '';
+    const nonce = nonceLine.split('Nonce:')[1]?.trim() || '';
+
+    const issuedAtLine = lines.find((line) => line.startsWith('Issued At:')) || '';
+    const issuedAt = issuedAtLine.split('Issued At:')[1]?.trim(); // Can't really be empty. Constructor will default to current date if not defined.
+    const issuedAtMilis = new Date(issuedAt).getTime();
+
+    const expirationTimeLine = lines.find((line) => line.startsWith('Expiration Time:')) || '';
+    const expirationTime = expirationTimeLine.split('Expiration Time:')[1]?.trim();
+    const expirationTimeMilis = new Date(expirationTime).getTime();
+
+    return new SignInMessage({
+      scheme: 'https',
+      domain,
+      address,
+      nonce,
+      expirationTime: expirationTimeMilis,
+      issuedAt: issuedAtMilis,
+    });
+  }
+}
+
+module.exports = { SignInMessage };
diff --git a/signer-service/src/api/middlewares/auth.js b/signer-service/src/api/middlewares/auth.js
new file mode 100644
index 00000000..614eab48
--- /dev/null
+++ b/signer-service/src/api/middlewares/auth.js
@@ -0,0 +1,77 @@
+const { validateSignatureAndGetMemo } = require('../services/siwe.service');
+
+const getMemoFromCookiesMiddleware = async (req, res, next) => {
+  // If the client didn't specify, we don't want to pass a derived memo even if a cookie was sent.
+
+  req.derivedMemo = null; // Explicit overwrite to avoid tampering, defensive.
+  if (!Boolean(req.body.usesMemo)) {
+    return next();
+  }
+  try {
+    const cookies = req.cookies;
+    const address = req.body.address;
+    // Default memo (represents no memo usage at all)
+    let resultMemo = null;
+
+    for (const authToken in cookies) {
+      if (!authToken.startsWith('authToken_')) {
+        continue;
+      }
+
+      //check if matches the address requested by client, otherwise ignore cookie.
+      if (!authToken.includes(address)) {
+        continue;
+      }
+
+      try {
+        const token = cookies[authToken];
+        const signature = token.signature;
+        const nonce = token.nonce;
+
+        if (!signature || !nonce) {
+          continue;
+        }
+
+        const memo = await validateSignatureAndGetMemo(nonce, signature);
+        console.log(memo);
+
+        // First found first used
+        if (memo) {
+          resultMemo = memo;
+          break;
+        }
+      } catch (e) {
+        continue;
+      }
+    }
+
+    // Client declared usage of memo, but it could not be derived from provided signatures.
+    if (Boolean(req.body.usesMemo) && !resultMemo) {
+      return res.status(401).json({
+        error: 'Missing or invalid authentication token',
+      });
+    }
+
+    req.derivedMemo = resultMemo;
+
+    next();
+  } catch (err) {
+    if (err.message.includes('Could not verify signature')) {
+      // Distinguish between failed signature check and other errors.
+      return res.status(401).json({
+        error: 'Signature validation failed.',
+        details: err.message,
+      });
+    }
+    console.error(`Error in getMemoFromCookiesMiddleware: ${err.message}`);
+
+    return res.status(500).json({
+      error: 'Error while verifying signature',
+      details: err.message,
+    });
+  }
+};
+
+module.exports = {
+  getMemoFromCookiesMiddleware,
+};
diff --git a/signer-service/src/api/routes/v1/stellar.route.js b/signer-service/src/api/routes/v1/stellar.route.js
index bc8f1d74..444e38ad 100644
--- a/signer-service/src/api/routes/v1/stellar.route.js
+++ b/signer-service/src/api/routes/v1/stellar.route.js
@@ -1,6 +1,7 @@
 const express = require('express');
 const controller = require('../../controllers/stellar.controller');
 const { validateCreationInput, validateChangeOpInput, validateSep10Input } = require('../../middlewares/validators');
+const { getMemoFromCookiesMiddleware } = require('../../middlewares/auth');
 
 const router = express.Router({ mergeParams: true });
 
@@ -8,7 +9,8 @@ router.route('/create').post(validateCreationInput, controller.createStellarTran
 
 router.route('/payment').post(validateChangeOpInput, controller.changeOpTransaction);
 
-router.route('/sep10').post(validateSep10Input, controller.signSep10Challenge);
+// Only authorized route. Does not reject the request, but rather passes the memo (if any) derived from a valid cookie in the request.
+router.route('/sep10').post([validateSep10Input, getMemoFromCookiesMiddleware], controller.signSep10Challenge);
 
 router.route('/sep10').get(controller.getSep10MasterPK);
 
diff --git a/signer-service/src/api/services/sep10.service.js b/signer-service/src/api/services/sep10.service.js
index 667b9408..e351172d 100644
--- a/signer-service/src/api/services/sep10.service.js
+++ b/signer-service/src/api/services/sep10.service.js
@@ -1,49 +1,19 @@
 const { Keypair } = require('stellar-sdk');
 const { TransactionBuilder, Networks } = require('stellar-sdk');
 const { fetchTomlValues } = require('../helpers/anchors');
-const { verifySiweMessage } = require('./siwe.service');
-const { keccak256 } = require('viem/utils');
 
 const { TOKEN_CONFIG } = require('../../constants/tokenConfig');
 const { SEP10_MASTER_SECRET, CLIENT_DOMAIN_SECRET } = require('../../constants/constants');
 
 const NETWORK_PASSPHRASE = Networks.PUBLIC;
 
-async function deriveMemoFromAddress(address) {
-  const hash = keccak256(address);
-  return BigInt(hash).toString().slice(0, 15);
-}
-
-// we validate a challenge for a given nonce. From it we obtain the address and derive the memo
-// we can then ensure that the memo is the same as the one we expect from the anchor challenge
-const validateSignatureAndGetMemo = async (nonce, userChallengeSignature, memoEnabled) => {
-  if (!userChallengeSignature || !nonce || !memoEnabled) {
-    return null; // Default memo value when single stellar account is used
-  }
-
-  let message;
-  try {
-    // initialSiweMessage must be undefined after an initial check,
-    // message must exist on the map.
-    message = await verifySiweMessage(nonce, userChallengeSignature, undefined);
-  } catch (e) {
-    throw new Error(`Could not verify signature: ${e.message}`);
-  }
-
-  const memo = await deriveMemoFromAddress(message.address);
-  return memo;
-};
-
-exports.signSep10Challenge = async (challengeXDR, outToken, clientPublicKey, userChallengeSignature, nonce) => {
+exports.signSep10Challenge = async (challengeXDR, outToken, clientPublicKey, memo) => {
   const masterStellarKeypair = Keypair.fromSecret(SEP10_MASTER_SECRET);
   const clientDomainStellarKeypair = Keypair.fromSecret(CLIENT_DOMAIN_SECRET);
 
   const { signingKey: anchorSigningKey } = await fetchTomlValues(TOKEN_CONFIG[outToken].tomlFileUrl);
   const { homeDomain, clientDomainEnabled, memoEnabled } = TOKEN_CONFIG[outToken];
 
-  // Expected memo based on user's signature and nonce.
-  const memo = await validateSignatureAndGetMemo(nonce, userChallengeSignature, memoEnabled);
-
   const transactionSigned = new TransactionBuilder.fromXDR(challengeXDR, NETWORK_PASSPHRASE);
   if (transactionSigned.source !== anchorSigningKey) {
     throw new Error(`Invalid source account: ${transactionSigned.source}`);
diff --git a/signer-service/src/api/services/siwe.service.js b/signer-service/src/api/services/siwe.service.js
index a3dda7a6..0b28f0c5 100644
--- a/signer-service/src/api/services/siwe.service.js
+++ b/signer-service/src/api/services/siwe.service.js
@@ -1,7 +1,11 @@
 const siwe = require('siwe');
 const { createPublicClient, http } = require('viem');
 const { polygon } = require('viem/chains');
-const { DEFAULT_LOGIN_EXPIRATION_TIME_HOURS, VALID_SIWE_CHAINS } = require('../../constants/constants');
+const { Keyring } = require('@polkadot/api');
+const { SignInMessage } = require('../helpers/siweMessageFormatter.js');
+const { signatureVerify } = require('@polkadot/util-crypto');
+const { deriveMemoFromAddress } = require('../helpers/memoDerivation');
+const { DEFAULT_LOGIN_EXPIRATION_TIME_HOURS } = require('../../constants/constants');
 
 class ValidationError extends Error {
   constructor(message) {
@@ -30,29 +34,34 @@ const verifySiweMessage = async (nonce, signature, initialSiweMessage) => {
 
   const siweMessage = existingSiweDataForNonce.siweMessage
     ? existingSiweDataForNonce.siweMessage
-    : new siwe.SiweMessage(initialSiweMessage);
+    : SignInMessage.fromMessage(initialSiweMessage);
   const address = existingSiweDataForNonce.address;
 
   if (!siweMessage) {
     throw new Error('Message must be provided as a parameter if it has not been initially validated.');
   }
 
-  // Verify the integrity of the message
-  const publicClient = createPublicClient({
-    chain: polygon,
-    transport: http(),
-  });
-
-  const valid = await publicClient.verifyMessage({
-    address: address,
-    message: siweMessage.toMessage(), // Validation must be done on the message as string
-    signature,
-  });
+  // verify with substrate (generic) or evm generic (using polygon public client)
+  let valid = false;
+  if (address.startsWith('0x')) {
+    const publicClient = createPublicClient({
+      chain: polygon,
+      transport: http(),
+    });
+    valid = await publicClient.verifyMessage({
+      address: address,
+      message: siweMessage.toMessage(), // Validation must be done on the message as string
+      signature,
+    });
+  } else if (address.startsWith('5')) {
+    valid = signatureVerify(siweMessage.toMessage(), signature, address);
+  } else {
+    throw new ValidationError(`verifySiweMessage: Invalid address format: ${address}`);
+  }
 
   if (!valid) {
     throw new ValidationError('Invalid signature');
   }
-
   // Perform additional checks to ensure message fields
   if (siweMessage.nonce !== nonce) {
     throw new ValidationError('Nonce mismatch');
@@ -68,16 +77,9 @@ const verifySiweMessage = async (nonce, signature, initialSiweMessage) => {
 // Since the message is created in the UI, we need to verify the fields of the message
 const verifyInitialMessageFields = (siweMessage) => {
   // Fields we validate on initial
-  const domain = siweMessage.domain;
-  const uri = siweMessage.uri;
   const scheme = siweMessage.scheme; // must be https
-  const chainId = siweMessage.chainId;
   const expirationTime = siweMessage.expirationTime;
 
-  if (!VALID_SIWE_CHAINS.includes(chainId)) {
-    throw new ValidationError('Incorrect chain ID');
-  }
-
   if (scheme !== 'https') {
     throw new ValidationError('Scheme must be https');
   }
@@ -122,6 +124,25 @@ const verifyAndStoreSiweMessage = async (nonce, signature, siweMessage) => {
       siweMessagesMap.delete(nonce);
     }
   });
+  return siweData.address;
+};
+
+const validateSignatureAndGetMemo = async (nonce, userChallengeSignature) => {
+  if (!userChallengeSignature || !nonce) {
+    return null; // Default memo value when single stellar account is used
+  }
+
+  let message;
+  try {
+    // initialSiweMessage must be undefined after an initial check,
+    // message must exist on the map.
+    message = await verifySiweMessage(nonce, userChallengeSignature, undefined);
+  } catch (e) {
+    throw new Error(`Could not verify signature: ${e.message}`);
+  }
+
+  const memo = await deriveMemoFromAddress(message.address);
+  return memo;
 };
 
-module.exports = { verifySiweMessage, verifyAndStoreSiweMessage, createAndSendNonce };
+module.exports = { verifySiweMessage, verifyAndStoreSiweMessage, createAndSendNonce, validateSignatureAndGetMemo };
diff --git a/signer-service/src/constants/constants.js b/signer-service/src/constants/constants.js
index ebac4e53..2dcb7bcc 100644
--- a/signer-service/src/constants/constants.js
+++ b/signer-service/src/constants/constants.js
@@ -9,7 +9,6 @@ const MOONBEAM_RECEIVER_CONTRACT_ADDRESS = '0x2AB52086e8edaB28193172209407FF9df1
 const STELLAR_EPHEMERAL_STARTING_BALANCE_UNITS = '2.5'; // Amount to send to the new stellar ephemeral account created
 const PENDULUM_EPHEMERAL_STARTING_BALANCE_UNITS = '0.1'; // Amount to send to the new pendulum ephemeral account created
 const DEFAULT_LOGIN_EXPIRATION_TIME_HOURS = 7 * 24;
-const VALID_SIWE_CHAINS = [137]; // 137: Polygon
 
 require('dotenv').config();
 
@@ -36,5 +35,4 @@ module.exports = {
   SEP10_MASTER_SECRET,
   CLIENT_DOMAIN_SECRET,
   DEFAULT_LOGIN_EXPIRATION_TIME_HOURS,
-  VALID_SIWE_CHAINS,
 };
diff --git a/src/contexts/siwe.tsx b/src/contexts/siwe.tsx
index 406a4c16..59336306 100644
--- a/src/contexts/siwe.tsx
+++ b/src/contexts/siwe.tsx
@@ -1,6 +1,5 @@
 import { createContext } from 'preact';
 import { PropsWithChildren, useContext } from 'preact/compat';
-import { useVortexAccount } from '../hooks/useVortexAccount';
 import { useSiweSignature } from '../hooks/useSignChallenge';
 
 type UseSiweContext = ReturnType<typeof useSiweSignature>;
@@ -16,8 +15,7 @@ export const useSiweContext = () => {
 };
 
 export const SiweProvider = ({ children }: PropsWithChildren) => {
-  const { address } = useVortexAccount();
-  const siweSignature = useSiweSignature(address);
+  const siweSignature = useSiweSignature();
 
   return <SiweContext.Provider value={siweSignature}>{children}</SiweContext.Provider>;
 };
diff --git a/src/helpers/siweMessageFormatter.ts b/src/helpers/siweMessageFormatter.ts
new file mode 100644
index 00000000..c4f94f0b
--- /dev/null
+++ b/src/helpers/siweMessageFormatter.ts
@@ -0,0 +1,66 @@
+interface SignInMessageFields {
+  scheme: string;
+  domain: string;
+  address: string;
+  nonce: string;
+  expirationTime: number;
+  issuedAt?: number;
+}
+
+export class SignInMessage {
+  public scheme: string;
+  public domain: string;
+  public address: string;
+  public nonce: string;
+  public expirationTime: string;
+  public issuedAt?: string;
+
+  static LOGIN_MESSAGE = ' wants you to sign in with your account: ';
+
+  constructor(fields: SignInMessageFields) {
+    this.scheme = fields.scheme;
+    this.domain = fields.domain;
+    this.address = fields.address;
+    this.nonce = fields.nonce;
+    this.expirationTime = new Date(fields.expirationTime).toISOString();
+    this.issuedAt = fields.issuedAt ? new Date(fields.issuedAt).toISOString() : new Date().toISOString();
+  }
+
+  public toMessage(): string {
+    const header = `${this.domain}${SignInMessage.LOGIN_MESSAGE}${this.address}`;
+
+    const body = `\nNonce: ${this.nonce}\nIssued At: ${this.issuedAt}\nExpiration Time: ${this.expirationTime}`;
+
+    return `${header}\n\n${body}`;
+  }
+
+  public static fromMessage(message: string): SignInMessage {
+    const lines = message
+      .split('\n')
+      .map((l) => l.trim())
+      .filter((l) => l.length > 0);
+
+    const headerLine = lines.find((line) => line.includes(SignInMessage.LOGIN_MESSAGE)) || '';
+    const [domain, address] = headerLine.split(SignInMessage.LOGIN_MESSAGE).map((part) => part.trim());
+
+    const nonceLine = lines.find((line) => line.startsWith('Nonce:')) || '';
+    const nonce = nonceLine.split('Nonce:')[1]?.trim() || '';
+
+    const issuedAtLine = lines.find((line) => line.startsWith('Issued At:')) || '';
+    const issuedAt = issuedAtLine.split('Issued At:')[1]?.trim(); // Can't really be empty. Constructor will default to current date if not defined.
+    const issuedAtMilis = new Date(issuedAt).getTime();
+
+    const expirationTimeLine = lines.find((line) => line.startsWith('Expiration Time:')) || '';
+    const expirationTime = expirationTimeLine.split('Expiration Time:')[1]?.trim();
+    const expirationTimeMilis = new Date(expirationTime).getTime();
+
+    return new SignInMessage({
+      scheme: 'https',
+      domain,
+      address,
+      nonce,
+      expirationTime: expirationTimeMilis,
+      issuedAt: issuedAtMilis,
+    });
+  }
+}
diff --git a/src/hooks/offramp/useSubmitOfframp.ts b/src/hooks/offramp/useSubmitOfframp.ts
index e8e466d0..70c1c5ad 100644
--- a/src/hooks/offramp/useSubmitOfframp.ts
+++ b/src/hooks/offramp/useSubmitOfframp.ts
@@ -80,6 +80,10 @@ export const useSubmitOfframp = ({
           const outputToken = OUTPUT_TOKEN_CONFIG[outputTokenType];
           const tomlValues = await fetchTomlValues(outputToken.tomlFileUrl!);
 
+          if (!address) {
+            throw new Error('useSubmitOfframp: Address must be defined at this stage');
+          }
+
           const { token: sep10Token, sep10Account } = await sep10(
             tomlValues,
             stellarEphemeralSecret,
diff --git a/src/hooks/useSignChallenge.ts b/src/hooks/useSignChallenge.ts
index c92390e3..6b56a68e 100644
--- a/src/hooks/useSignChallenge.ts
+++ b/src/hooks/useSignChallenge.ts
@@ -1,11 +1,10 @@
 import { useState, useCallback } from 'preact/compat';
-import { useSignMessage } from 'wagmi';
-import { polygon } from 'wagmi/chains';
-import { SiweMessage } from 'siwe';
+import { SignInMessage } from '../helpers/siweMessageFormatter';
 
 import { DEFAULT_LOGIN_EXPIRATION_TIME_HOURS } from '../constants/constants';
 import { SIGNING_SERVICE_URL } from '../constants/constants';
 import { storageKeys } from '../constants/localStorage';
+import { useVortexAccount } from './useVortexAccount';
 
 export interface SiweSignatureData {
   signatureSet: boolean;
@@ -13,24 +12,20 @@ export interface SiweSignatureData {
 }
 
 function createSiweMessage(address: string, nonce: string) {
-  // Make constants on config
-  const siweMessage = new SiweMessage({
+  const siweMessage = new SignInMessage({
     scheme: 'https',
     domain: window.location.host,
-    address,
-    statement: 'Please sign the message to login!',
-    uri: window.location.origin,
-    version: '1',
-    chainId: polygon.id,
+    address: address,
     nonce,
-    expirationTime: new Date(Date.now() + DEFAULT_LOGIN_EXPIRATION_TIME_HOURS * 60 * 60 * 1000).toISOString(), // Constructor in ms.
+    expirationTime: new Date(Date.now() + DEFAULT_LOGIN_EXPIRATION_TIME_HOURS * 60 * 60 * 1000).getTime(), // Constructor in ms.
   });
+
   return siweMessage.toMessage();
 }
 
-export function useSiweSignature(address?: string) {
-  const { signMessageAsync } = useSignMessage();
+export function useSiweSignature() {
   const [signingPending, setSigningPending] = useState(false);
+  const { address, getMessageSignature } = useVortexAccount();
 
   // Used to wait for the modal interaction and/or return of the
   // signing promise.
@@ -78,10 +73,11 @@ export function useSiweSignature(address?: string) {
       if (!messageResponse.ok) throw new Error('Failed to create message');
       const { nonce } = await messageResponse.json();
 
+      // Message in both string and object form
       const siweMessage = createSiweMessage(address, nonce);
+      const message = SignInMessage.fromMessage(siweMessage);
 
-      const message = new SiweMessage(siweMessage);
-      const signature = await signMessageAsync({ message: siweMessage });
+      const signature = await getMessageSignature(siweMessage);
 
       const validationResponse = await fetch(`${SIGNING_SERVICE_URL}/v1/siwe/validate`, {
         method: 'POST',
@@ -106,7 +102,7 @@ export function useSiweSignature(address?: string) {
       setSigningPending(false);
       setSignPromise(null);
     }
-  }, [address, storageKey, signMessageAsync, signPromise, setSigningPending, setSignPromise]);
+  }, [address, storageKey, signPromise, setSigningPending, setSignPromise, getMessageSignature]);
 
   // Handler for modal cancellation
   const handleCancel = useCallback(() => {
diff --git a/src/hooks/useVortexAccount.ts b/src/hooks/useVortexAccount.ts
index 362bcb21..7c9b3488 100644
--- a/src/hooks/useVortexAccount.ts
+++ b/src/hooks/useVortexAccount.ts
@@ -1,7 +1,9 @@
 import { Networks, useNetwork } from '../contexts/network';
-import { useMemo } from 'preact/compat';
+import { useMemo, useCallback } from 'preact/compat';
 import { usePolkadotWalletState } from '../contexts/polkadotWallet';
 import { useAccount } from 'wagmi';
+import { Signer } from '@polkadot/types/types';
+import { useSignMessage } from 'wagmi';
 
 // For the AssetHub network, we use a chain ID of -1. This is not a valid chain ID
 // but we just use it to differentiate between the EVM and Polkadot accounts.
@@ -14,6 +16,7 @@ export const useVortexAccount = () => {
 
   const { walletAccount: polkadotWalletAccount } = usePolkadotWalletState();
   const { isDisconnected: isEvmAccountDisconnected, chainId: evmChainId, address: evmAccountAddress } = useAccount();
+  const { signMessageAsync } = useSignMessage();
 
   const address = useMemo(() => {
     if (selectedNetwork === Networks.AssetHub) {
@@ -47,10 +50,36 @@ export const useVortexAccount = () => {
     }
   }, [selectedNetwork]);
 
+  const getMessageSignature = useCallback(
+    async (siweMessage: string) => {
+      let signature;
+
+      if (selectedNetwork === Networks.Polygon) {
+        signature = await signMessageAsync({ message: siweMessage });
+      } else if (selectedNetwork === Networks.AssetHub) {
+        if (!polkadotWalletAccount) {
+          throw new Error('getMessageSignature: Polkadot wallet account not found. Wallet must be connected to sign.');
+        }
+        const { signature: substrateSignature } = await (polkadotWalletAccount.signer as Signer).signRaw!({
+          type: 'payload',
+          data: siweMessage,
+          address: polkadotWalletAccount.address,
+        });
+        signature = substrateSignature;
+      } else {
+        throw new Error('getMessageSignature: Unsupported network.');
+      }
+
+      return signature;
+    },
+    [polkadotWalletAccount, selectedNetwork, signMessageAsync],
+  );
+
   return {
     isDisconnected,
     chainId,
     address,
     type,
+    getMessageSignature,
   };
 };
diff --git a/src/services/anchor/index.ts b/src/services/anchor/index.ts
index 9044da05..721d9426 100644
--- a/src/services/anchor/index.ts
+++ b/src/services/anchor/index.ts
@@ -75,7 +75,7 @@ function getHashValueForAddress(address: string) {
   }
 }
 
-//A memo derivation. TODO: Secure? how to check for collisions?
+//A memo derivation.
 async function deriveMemoFromAddress(address: string) {
   const hashValue = getHashValueForAddress(address);
   const hash = keccak256(hashValue);
@@ -142,7 +142,7 @@ export const sep10 = async (
   tomlValues: TomlValues,
   stellarEphemeralSecret: string,
   outputToken: OutputTokenType,
-  address: string | undefined,
+  address: string,
   checkAndWaitForSignature: () => Promise<void>,
   forceRefreshAndWaitForSignature: () => Promise<void>,
   renderEvent: (event: string, status: EventStatus) => void,
@@ -150,7 +150,7 @@ export const sep10 = async (
   const { signingKey, webAuthEndpoint } = tomlValues;
 
   if (!exists(signingKey) || !exists(webAuthEndpoint)) {
-    throw new Error('Missing values in TOML file');
+    throw new Error('sep10: Missing values in TOML file');
   }
   const NETWORK_PASSPHRASE = Networks.PUBLIC;
   const ephemeralKeys = Keypair.fromSecret(stellarEphemeralSecret);
@@ -159,24 +159,24 @@ export const sep10 = async (
   const { usesMemo, supportsClientDomain } = OUTPUT_TOKEN_CONFIG[outputToken];
 
   // will select either clientMaster or the ephemeral account
-  const { urlParams, sep10Account } = await getUrlParams(accountId, usesMemo, supportsClientDomain, address!);
+  const { urlParams, sep10Account } = await getUrlParams(accountId, usesMemo, supportsClientDomain, address);
 
   const challenge = await fetch(`${webAuthEndpoint}?${urlParams.toString()}`);
   if (challenge.status !== 200) {
-    throw new Error(`Failed to fetch SEP-10 challenge: ${challenge.statusText}`);
+    throw new Error(`sep10: Failed to fetch SEP-10 challenge: ${challenge.statusText}`);
   }
 
   const { transaction, network_passphrase } = await challenge.json();
   if (network_passphrase !== NETWORK_PASSPHRASE) {
-    throw new Error(`Invalid network passphrase: ${network_passphrase}`);
+    throw new Error(`sep10: Invalid network passphrase: ${network_passphrase}`);
   }
 
   const transactionSigned = new Transaction(transaction, NETWORK_PASSPHRASE);
   if (transactionSigned.source !== signingKey) {
-    throw new Error(`Invalid source account: ${transactionSigned.source}`);
+    throw new Error(`sep10: Invalid source account: ${transactionSigned.source}`);
   }
   if (transactionSigned.sequence !== '0') {
-    throw new Error(`Invalid sequence number: ${transactionSigned.sequence}`);
+    throw new Error(`sep10: Invalid sequence number: ${transactionSigned.sequence}`);
   }
 
   if (usesMemo) {
@@ -189,7 +189,8 @@ export const sep10 = async (
       challengeXDR: transactionSigned.toXDR(),
       outToken: outputToken,
       clientPublicKey: sep10Account,
-      memo: usesMemo,
+      usesMemo,
+      address: address,
     },
   );
 
diff --git a/src/services/signingService.tsx b/src/services/signingService.tsx
index d70237a5..8ba7f28e 100644
--- a/src/services/signingService.tsx
+++ b/src/services/signingService.tsx
@@ -22,7 +22,8 @@ export interface SignerServiceSep10Request {
   challengeXDR: string;
   outToken: OutputTokenType;
   clientPublicKey: string;
-  memo?: boolean;
+  address: string;
+  usesMemo?: boolean;
 }
 
 // @todo: implement @tanstack/react-query
@@ -51,13 +52,14 @@ export const fetchSep10Signatures = async ({
   challengeXDR,
   outToken,
   clientPublicKey,
-  memo,
+  usesMemo,
+  address,
 }: SignerServiceSep10Request): Promise<SignerServiceSep10Response> => {
   const response = await fetch(`${SIGNING_SERVICE_URL}/v1/stellar/sep10`, {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
     credentials: 'include',
-    body: JSON.stringify({ challengeXDR, outToken, clientPublicKey, memo }),
+    body: JSON.stringify({ challengeXDR, outToken, clientPublicKey, usesMemo, address }),
   });
   if (response.status !== 200) {
     if (response.status === 401) {
diff --git a/yarn.lock b/yarn.lock
index e4afabb4..15df6d94 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -12,13 +12,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@adraffy/ens-normalize@npm:1.10.1":
-  version: 1.10.1
-  resolution: "@adraffy/ens-normalize@npm:1.10.1"
-  checksum: 10/4cb938c4abb88a346d50cb0ea44243ab3574330c81d4f5aaaf9dfee584b96189d0faa404de0fcbef5a1b73909ea4ebc3e63d84bd23f9949e5c8d4085207a5091
-  languageName: node
-  linkType: hard
-
 "@adraffy/ens-normalize@npm:^1.10.1, @adraffy/ens-normalize@npm:^1.8.8":
   version: 1.11.0
   resolution: "@adraffy/ens-normalize@npm:1.11.0"
@@ -2874,7 +2867,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@noble/hashes@npm:1.5.0, @noble/hashes@npm:^1.1.2, @noble/hashes@npm:^1.4.0, @noble/hashes@npm:^1.5.0, @noble/hashes@npm:~1.5.0":
+"@noble/hashes@npm:1.5.0, @noble/hashes@npm:^1.4.0, @noble/hashes@npm:^1.5.0, @noble/hashes@npm:~1.5.0":
   version: 1.5.0
   resolution: "@noble/hashes@npm:1.5.0"
   checksum: 10/da7fc7af52af7afcf59810a7eea6155075464ff462ffda2572dc6d57d53e2669b1ea2ec774e814f6273f1697e567f28d36823776c9bf7068cba2a2855140f26e
@@ -4429,18 +4422,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@spruceid/siwe-parser@npm:^2.1.2":
-  version: 2.1.2
-  resolution: "@spruceid/siwe-parser@npm:2.1.2"
-  dependencies:
-    "@noble/hashes": "npm:^1.1.2"
-    apg-js: "npm:^4.3.0"
-    uri-js: "npm:^4.4.1"
-    valid-url: "npm:^1.0.9"
-  checksum: 10/48459fe3b4d4b3091375ee87af700864c9023d4a1271d34850c6d27475e5d93a45d1efe8a71da367ad838b6921ced60c387d54737edd0a7a0d8e4e0a3cc2b8b7
-  languageName: node
-  linkType: hard
-
 "@stablelib/aead@npm:^1.0.1":
   version: 1.0.1
   resolution: "@stablelib/aead@npm:1.0.1"
@@ -4859,19 +4840,19 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@types/node@npm:*, @types/node@npm:^18.14.1":
+"@types/node@npm:*":
   version: 18.16.3
   resolution: "@types/node@npm:18.16.3"
   checksum: 10/4f4425ba49a46e7efa88346dc2ea63ea9aab88c04d244d77710fe8019587f3c163ba2ea1e4854fd20cb5cdec9abd3bfb324ad60aabddf395cee6b0b195bd57bb
   languageName: node
   linkType: hard
 
-"@types/node@npm:22.7.5":
-  version: 22.7.5
-  resolution: "@types/node@npm:22.7.5"
+"@types/node@npm:^22.7.5":
+  version: 22.10.2
+  resolution: "@types/node@npm:22.10.2"
   dependencies:
-    undici-types: "npm:~6.19.2"
-  checksum: 10/e8ba102f8c1aa7623787d625389be68d64e54fcbb76d41f6c2c64e8cf4c9f4a2370e7ef5e5f1732f3c57529d3d26afdcb2edc0101c5e413a79081449825c57ac
+    undici-types: "npm:~6.20.0"
+  checksum: 10/451adfefed4add58b069407173e616220fd4aaa3307cdde1bb701aa053b65b54ced8483db2f870dcedec7a58cb3b06101fbc19d85852716672ec1fd3660947fa
   languageName: node
   linkType: hard
 
@@ -5764,13 +5745,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"aes-js@npm:4.0.0-beta.5":
-  version: 4.0.0-beta.5
-  resolution: "aes-js@npm:4.0.0-beta.5"
-  checksum: 10/8f745da2e8fb38e91297a8ec13c2febe3219f8383303cd4ed4660ca67190242ccfd5fdc2f0d1642fd1ea934818fb871cd4cc28d3f28e812e3dc6c3d0f1f97c24
-  languageName: node
-  linkType: hard
-
 "agent-base@npm:6, agent-base@npm:^6.0.2":
   version: 6.0.2
   resolution: "agent-base@npm:6.0.2"
@@ -5901,13 +5875,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"apg-js@npm:^4.3.0":
-  version: 4.4.0
-  resolution: "apg-js@npm:4.4.0"
-  checksum: 10/425f19096026742f5f156f26542b68f55602aa60f0c4ae2d72a0a888cf15fe9622223191202262dd8979d76a6125de9d8fd164d56c95fb113f49099f405eb08c
-  languageName: node
-  linkType: hard
-
 "app-root-path@npm:2.1.0":
   version: 2.1.0
   resolution: "app-root-path@npm:2.1.0"
@@ -8567,21 +8534,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"ethers@npm:^6.13.4":
-  version: 6.13.4
-  resolution: "ethers@npm:6.13.4"
-  dependencies:
-    "@adraffy/ens-normalize": "npm:1.10.1"
-    "@noble/curves": "npm:1.2.0"
-    "@noble/hashes": "npm:1.3.2"
-    "@types/node": "npm:22.7.5"
-    aes-js: "npm:4.0.0-beta.5"
-    tslib: "npm:2.7.0"
-    ws: "npm:8.17.1"
-  checksum: 10/221192fed93f6b0553f3e5e72bfd667d676220577d34ff854f677e955d6f608e60636a9c08b5d54039c532a9b9b7056384f0d7019eb6e111d53175806f896ac6
-  languageName: node
-  linkType: hard
-
 "event-emitter@npm:^0.3.5":
   version: 0.3.5
   resolution: "event-emitter@npm:0.3.5"
@@ -13422,20 +13374,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"siwe@npm:^2.3.2":
-  version: 2.3.2
-  resolution: "siwe@npm:2.3.2"
-  dependencies:
-    "@spruceid/siwe-parser": "npm:^2.1.2"
-    "@stablelib/random": "npm:^1.0.1"
-    uri-js: "npm:^4.4.1"
-    valid-url: "npm:^1.0.9"
-  peerDependencies:
-    ethers: ^5.6.8 || ^6.0.8
-  checksum: 10/6ea5ad9a9046fa916f85bf9d3092bc898f7e339d9c552714ea53ecc17daa4f78300c3cf7cc9c70fe57baf77dcee5cb38c6e1d692400b874cd84d297b1261918c
-  languageName: node
-  linkType: hard
-
 "slash@npm:^3.0.0":
   version: 3.0.0
   resolution: "slash@npm:3.0.0"
@@ -14249,13 +14187,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"tslib@npm:2.7.0, tslib@npm:^2.7.0":
-  version: 2.7.0
-  resolution: "tslib@npm:2.7.0"
-  checksum: 10/9a5b47ddac65874fa011c20ff76db69f97cf90c78cff5934799ab8894a5342db2d17b4e7613a087046bc1d133d21547ddff87ac558abeec31ffa929c88b7fce6
-  languageName: node
-  linkType: hard
-
 "tslib@npm:^2.0.0, tslib@npm:^2.4.0":
   version: 2.6.3
   resolution: "tslib@npm:2.6.3"
@@ -14277,6 +14208,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"tslib@npm:^2.7.0":
+  version: 2.7.0
+  resolution: "tslib@npm:2.7.0"
+  checksum: 10/9a5b47ddac65874fa011c20ff76db69f97cf90c78cff5934799ab8894a5342db2d17b4e7613a087046bc1d133d21547ddff87ac558abeec31ffa929c88b7fce6
+  languageName: node
+  linkType: hard
+
 "tsscmp@npm:^1.0.5":
   version: 1.0.6
   resolution: "tsscmp@npm:1.0.6"
@@ -14483,10 +14421,10 @@ __metadata:
   languageName: node
   linkType: hard
 
-"undici-types@npm:~6.19.2":
-  version: 6.19.8
-  resolution: "undici-types@npm:6.19.8"
-  checksum: 10/cf0b48ed4fc99baf56584afa91aaffa5010c268b8842f62e02f752df209e3dea138b372a60a963b3b2576ed932f32329ce7ddb9cb5f27a6c83040d8cd74b7a70
+"undici-types@npm:~6.20.0":
+  version: 6.20.0
+  resolution: "undici-types@npm:6.20.0"
+  checksum: 10/583ac7bbf4ff69931d3985f4762cde2690bb607844c16a5e2fbb92ed312fe4fa1b365e953032d469fa28ba8b224e88a595f0b10a449332f83fa77c695e567dbe
   languageName: node
   linkType: hard
 
@@ -14699,7 +14637,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"uri-js@npm:^4.2.2, uri-js@npm:^4.4.1":
+"uri-js@npm:^4.2.2":
   version: 4.4.1
   resolution: "uri-js@npm:4.4.1"
   dependencies:
@@ -14834,13 +14772,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"valid-url@npm:^1.0.9":
-  version: 1.0.9
-  resolution: "valid-url@npm:1.0.9"
-  checksum: 10/343dfaf85eb3691dc8eb93f7bc007be1ee6091e6c6d1a68bf633cb85e4bf2930e34ca9214fb2c3330de5b652510b257a8ee1ff0a0a37df0925e9dabf93ee512d
-  languageName: node
-  linkType: hard
-
 "valtio@npm:1.11.2":
   version: 1.11.2
   resolution: "valtio@npm:1.11.2"
@@ -15142,7 +15073,7 @@ __metadata:
     "@tanstack/react-query": "npm:^5.61.0"
     "@types/big.js": "npm:^6"
     "@types/bn.js": "npm:^5"
-    "@types/node": "npm:^18.14.1"
+    "@types/node": "npm:^22.7.5"
     "@types/react": "npm:^18.3.10"
     "@typescript-eslint/eslint-plugin": "npm:^5.53.0"
     "@typescript-eslint/parser": "npm:^5.53.0"
@@ -15157,7 +15088,6 @@ __metadata:
     eslint: "npm:^8.34.0"
     eslint-plugin-react: "npm:^7.32.2"
     eslint-plugin-react-hooks: "npm:^4.6.0"
-    ethers: "npm:^6.13.4"
     framer-motion: "npm:^11.2.14"
     happy-dom: "npm:^14.12.3"
     husky: "npm:>=6"
@@ -15171,7 +15101,6 @@ __metadata:
     react-hook-form: "npm:^7.51.5"
     react-router-dom: "npm:^6.8.1"
     react-toastify: "npm:^10.0.6"
-    siwe: "npm:^2.3.2"
     stellar-base: "npm:^11.0.1"
     stellar-sdk: "npm:^11.3.0"
     tailwind: "npm:^4.0.0"