diff --git a/package.json b/package.json
index 644b53ae..d169c475 100644
--- a/package.json
+++ b/package.json
@@ -12,6 +12,7 @@
     "lint": "eslint . --max-warnings=0",
     "perf:budgets": "node scripts/check-performance-budgets.mjs",
     "perf:ci": "npm run build && npm run perf:budgets",
+    "security:check-globals": "node scripts/check-exposed-globals.mjs",
     "validate:env": "node scripts/validate-env.js",
     "storybook": "storybook dev -p 6006",
     "build-storybook": "storybook build",
diff --git a/scripts/check-exposed-globals.mjs b/scripts/check-exposed-globals.mjs
new file mode 100644
index 00000000..aef1dfe0
--- /dev/null
+++ b/scripts/check-exposed-globals.mjs
@@ -0,0 +1,37 @@
+import { readFileSync, existsSync } from 'fs';
+import { glob } from 'glob';
+
+const SENSITIVE_PATTERNS = [
+  /__[A-Z][A-Z_]+__/g,
+];
+
+async function main() {
+  const files = await glob('src/**/*.{ts,tsx,js,jsx}', {
+    ignore: ['src/**/*.test.*', 'src/**/__tests__/**', 'node_modules/**'],
+  });
+
+  let hasError = false;
+
+  for (const file of files) {
+    if (!existsSync(file)) continue;
+    const content = readFileSync(file, 'utf-8');
+    const matches = content.match(SENSITIVE_PATTERNS[0]);
+    if (matches) {
+      for (const match of matches) {
+        console.error(`[FAIL] Found exposed global '${match}' in ${file}`);
+        hasError = true;
+      }
+    }
+  }
+
+  if (hasError) {
+    process.exit(1);
+  }
+
+  console.log('[PASS] No exposed globals found.');
+}
+
+main().catch((err) => {
+  console.error('Script failed:', err);
+  process.exit(1);
+});
diff --git a/src/app/api/security/address-check/route.ts b/src/app/api/security/address-check/route.ts
new file mode 100644
index 00000000..e934afe4
--- /dev/null
+++ b/src/app/api/security/address-check/route.ts
@@ -0,0 +1,54 @@
+import { NextRequest, NextResponse } from 'next/server';
+
+export async function GET(request: NextRequest) {
+  const { searchParams } = new URL(request.url);
+  const address = searchParams.get('address')?.trim();
+
+  if (!address) {
+    return NextResponse.json({ error: 'Address parameter required' }, { status: 400 });
+  }
+
+  if (!/^0x[a-fA-F0-9]{40}$/.test(address)) {
+    return NextResponse.json({ error: 'Invalid Ethereum address' }, { status: 400 });
+  }
+
+  const apiKey = process.env.CHAINALYSIS_API_KEY;
+
+  if (!apiKey) {
+    return NextResponse.json({
+      address,
+      risk_score: 50,
+      categories: ['unknown'],
+      description: 'Risk check unavailable (service not configured)',
+    });
+  }
+
+  try {
+    const response = await fetch(
+      `https://api.chainalysis.com/api/v2/address/${address}`,
+      {
+        headers: {
+          Authorization: `Bearer ${apiKey}`,
+          'Content-Type': 'application/json',
+        },
+        signal: AbortSignal.timeout(10000),
+      }
+    );
+
+    if (!response.ok) {
+      const errorText = await response.text();
+      return NextResponse.json(
+        { error: `Upstream service error: ${response.status}`, detail: errorText },
+        { status: response.status }
+      );
+    }
+
+    const data = await response.json();
+    return NextResponse.json(data);
+  } catch (error) {
+    return NextResponse.json(
+      { error: error instanceof Error ? error.message : 'Unknown error' },
+      { status: 502 }
+    );
+  }
+}
diff --git a/src/components/ui/chart.tsx b/src/components/ui/chart.tsx
index e04abd79..20b00868 100644
--- a/src/components/ui/chart.tsx
+++ b/src/components/ui/chart.tsx
@@ -78,28 +78,27 @@ const ChartStyle = ({ id, config }: { id: string; config: ChartConfig }) => {
     return null
   }
 
-  return (
-    <style
-      dangerouslySetInnerHTML={{
-        __html: Object.entries(THEMES)
-          .map(
-            ([theme, prefix]) => `
-${prefix} [data-chart=${id}] {
-${colorConfig
-  .map(([key, itemConfig]) => {
-    const color =
-      itemConfig.theme?.[theme as keyof typeof itemConfig.theme] ||
-      itemConfig.color
-    return color ? `  --color-${key}: ${color};` : null
-  })
-  .join("\n")}
-}
-`
-          )
-          .join("\n"),
-      }}
-    />
-  )
+  const cssContent = Object.entries(THEMES)
+    .map(([theme, prefix]) => {
+      const rules = colorConfig
+        .map(([key, itemConfig]) => {
+          const color =
+            itemConfig.theme?.[theme as keyof typeof itemConfig.theme] ||
+            itemConfig.color
+          return color ? `  --color-${key}: ${color};` : null
+        })
+        .filter(Boolean)
+        .join("\n")
+      return rules ? `${prefix} [data-chart=${id}] {\n${rules}\n}` : ""
+    })
+    .filter(Boolean)
+    .join("\n")
+
+  if (!cssContent) {
+    return null
+  }
+
+  return <style>{cssContent}</style>
 }
 
 const ChartTooltip = Tooltip
diff --git a/src/utils/security/__tests__/blockchainSecurity.test.ts b/src/utils/security/__tests__/blockchainSecurity.test.ts
index 54b19492..f9c8dbab 100644
--- a/src/utils/security/__tests__/blockchainSecurity.test.ts
+++ b/src/utils/security/__tests__/blockchainSecurity.test.ts
@@ -6,9 +6,9 @@ global.fetch = jest.fn();
 describe('BlockchainSecurityService', () => {
   let service: BlockchainSecurityService;
   const mockConfig: SecurityServiceConfig = {
-    baseUrl: 'https://api.test.com',
+    baseUrl: 'http://localhost:3000',
     timeout: 5000,
-    apiKey: 'test-api-key'
+    apiKey: undefined
   };
 
   beforeEach(() => {
@@ -89,8 +89,33 @@ describe('BlockchainSecurityService', () => {
       expect(result.riskScore).toBeGreaterThan(0);
     });
 
+    it('should call the local proxy endpoint', async () => {
+      (global.fetch as jest.Mock).mockResolvedValueOnce({
+        ok: true,
+        json: async () => ({ risk_score: 30, categories: ['low_risk'], labels: [], description: 'Normal' })
+      });
+
+      await service.checkAddressRisk(testAddress);
+
+      const fetchUrl = (global.fetch as jest.Mock).mock.calls[0][0];
+      expect(fetchUrl).toContain('/api/security/address-check');
+      expect(fetchUrl).toContain(encodeURIComponent(testAddress));
+    });
+
+    it('should fall back to simulation when proxy returns non-ok', async () => {
+      (global.fetch as jest.Mock).mockResolvedValueOnce({
+        ok: false,
+        status: 502,
+        json: async () => ({ error: 'Bad gateway' })
+      });
+
+      const result = await service.checkAddressRisk(testAddress);
+      expect(result.riskScore).toBeGreaterThanOrEqual(0);
+      expect(result.riskScore).toBeLessThanOrEqual(100);
+    });
+
     it('should return default risk score on API failure', async () => {
-      (global.fetch as jest.Mock).mockRejectedValueOnce(new Error('API Error'));
+      (global.fetch as jest.Mock).mockRejectedValueOnce(new Error('Network error'));
 
       const result = await service.checkAddressRisk(testAddress);
       expect(result).toEqual({
diff --git a/src/utils/security/__tests__/transactionSecurity.test.ts b/src/utils/security/__tests__/transactionSecurity.test.ts
index da3014bb..ec162264 100644
--- a/src/utils/security/__tests__/transactionSecurity.test.ts
+++ b/src/utils/security/__tests__/transactionSecurity.test.ts
@@ -1,6 +1,10 @@
-import { decideStepUpSecurity, ethToWei } from '../transactionSecurity';
+import { decideStepUpSecurity, ethToWei, getSecurityDeviceId } from '../transactionSecurity';
 
 describe('transactionSecurity helpers', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
   it('requires step-up for values at or above the configured threshold', () => {
     const decision = decideStepUpSecurity({
       valueWei: ethToWei(3),
@@ -39,5 +43,82 @@ describe('transactionSecurity helpers', () => {
     expect(decision.requiresStepUp).toBe(false);
     expect(decision.reason).toBeNull();
   });
+
+  describe('getSecurityDeviceId', () => {
+    let mockLocalStorage: Record<string, string>;
+    let mockSessionStorage: Record<string, string>;
+
+    beforeEach(() => {
+      mockLocalStorage = {};
+      mockSessionStorage = {};
+      jest.spyOn(globalThis, 'crypto', 'get').mockReturnValue({
+        randomUUID: () => '550e8400-e29b-41d4-a716-446655440000',
+        subtle: {} as SubtleCrypto,
+        getRandomValues: (arr: Uint8Array) => arr,
+      } as unknown as Crypto);
+      jest.spyOn(globalThis, 'localStorage', 'get').mockReturnValue({
+        getItem: (key: string) => mockLocalStorage[key] ?? null,
+        setItem: (key: string, value: string) => { mockLocalStorage[key] = value; },
+        removeItem: (key: string) => { delete mockLocalStorage[key]; },
+        clear: () => { mockLocalStorage = {}; },
+        get length() { return Object.keys(mockLocalStorage).length; },
+        key: (index: number) => Object.keys(mockLocalStorage)[index] ?? null,
+      } as Storage);
+      jest.spyOn(globalThis, 'sessionStorage', 'get').mockReturnValue({
+        getItem: (key: string) => mockSessionStorage[key] ?? null,
+        setItem: (key: string, value: string) => { mockSessionStorage[key] = value; },
+        removeItem: (key: string) => { delete mockSessionStorage[key]; },
+        clear: () => { mockSessionStorage = {}; },
+        get length() { return Object.keys(mockSessionStorage).length; },
+        key: (index: number) => Object.keys(mockSessionStorage)[index] ?? null,
+      } as Storage);
+    });
+
+    afterEach(() => {
+      jest.restoreAllMocks();
+    });
+
+    it('returns "server-device" when window is undefined', () => {
+      const windowSpy = jest.spyOn(globalThis, 'window', 'get').mockReturnValue(undefined as any);
+      expect(getSecurityDeviceId()).toBe('server-device');
+      windowSpy.mockRestore();
+    });
+
+    it('generates and stores a salted hash on first call', () => {
+      const result = getSecurityDeviceId();
+
+      expect(result).toBe('550e8400-e29b-41d4-a716-446655440000');
+      expect(mockSessionStorage['propchain-session-salt']).toBeDefined();
+      expect(mockLocalStorage['propchain-security-device-id-hash']).toBeDefined();
+      expect(mockLocalStorage['propchain-security-device-id-hash']).not.toBe(result);
+    });
+
+    it('reuses existing hash from localStorage on subsequent calls', () => {
+      const existingHash = 'a1b2c3d4';
+      mockLocalStorage['propchain-security-device-id-hash'] = existingHash;
+
+      const result = getSecurityDeviceId();
+
+      expect(result).toBe(existingHash);
+      expect(mockSessionStorage['propchain-session-salt']).toBeUndefined();
+    });
+
+    it('reuses session salt across calls within the same session', () => {
+      const sessionSalt = 'test-session-salt';
+      mockSessionStorage['propchain-session-salt'] = sessionSalt;
+
+      getSecurityDeviceId();
+
+      expect(mockSessionStorage['propchain-session-salt']).toBe(sessionSalt);
+    });
+
+    it('stores a hashed value, not the raw UUID', () => {
+      getSecurityDeviceId();
+
+      const storedValue = mockLocalStorage['propchain-security-device-id-hash'];
+      expect(storedValue).not.toBe('550e8400-e29b-41d4-a716-446655440000');
+      expect(storedValue).toMatch(/^[0-9a-f]{8,}$/);
+    });
+  });
 });
 
diff --git a/src/utils/security/blockchainSecurity.ts b/src/utils/security/blockchainSecurity.ts
index f022d259..a1cb7490 100644
--- a/src/utils/security/blockchainSecurity.ts
+++ b/src/utils/security/blockchainSecurity.ts
@@ -74,35 +74,42 @@ export class BlockchainSecurityService {
     if (cached) return cached;
 
     try {
-      // Try calling a remote API if available. If `fetch` returns a Promise
-      // (for example when tests mock it), await it and use the response.
-      // Otherwise, fall back to the local simulation to preserve test behavior.
-      const fetchResult = typeof fetch === 'function' ? (fetch as any)(`${this.config.baseUrl}/address/${address}`, {
-        headers: this.config.apiKey ? { Authorization: `Bearer ${this.config.apiKey}` } : {}
-      }) : null;
-
-      if (fetchResult && typeof fetchResult.then === 'function') {
-        const response = await fetchResult;
-        if (response && response.ok) {
-          const body = await response.json();
-          const score = typeof body.risk_score === 'number' ? body.risk_score : 50;
-          const categories = Array.isArray(body.categories) ? body.categories : [];
-          const result: AddressRiskScore = {
-            address,
-            riskScore: score,
-            riskLevel: this.getRiskLevel(score),
-            categories,
-            labels: Array.isArray(body.labels) ? body.labels : [],
-            description: body.description || ''
-          };
-          this.setCache(cacheKey, result);
-          return result;
-        }
-        // If response not ok, throw to be caught below and return default
-        throw new Error('Remote service returned non-OK response');
+      // Call the local API proxy route which securely holds the API key server-side.
+      // This avoids exposing the key in the client bundle.
+      const baseUrl = typeof window !== 'undefined'
+        ? window.location.origin
+        : this.config.baseUrl;
+
+      const controller = new AbortController();
+      const timeoutId = setTimeout(() => controller.abort(), this.config.timeout);
+
+      let response;
+      try {
+        response = await fetch(
+          `${baseUrl}/api/security/address-check?address=${encodeURIComponent(address)}`,
+          { signal: controller.signal }
+        );
+      } finally {
+        clearTimeout(timeoutId);
       }
 
-      // No remote fetch available — use the internal simulation
+      if (response && response.ok) {
+        const body = await response.json();
+        const score = typeof body.risk_score === 'number' ? body.risk_score : 50;
+        const categories = Array.isArray(body.categories) ? body.categories : [];
+        const result: AddressRiskScore = {
+          address,
+          riskScore: score,
+          riskLevel: this.getRiskLevel(score),
+          categories,
+          labels: Array.isArray(body.labels) ? body.labels : [],
+          description: body.description || ''
+        };
+        this.setCache(cacheKey, result);
+        return result;
+      }
+
+      // If the proxy returned an error or is unavailable, fall back to simulated check
       const riskScore = await this.simulateAddressRiskCheck(address);
 
       const result: AddressRiskScore = {
@@ -494,10 +501,11 @@ export class BlockchainSecurityService {
 
 // Default configuration for development
 const defaultConfig: SecurityServiceConfig = {
-  baseUrl: 'https://api.chainalysis.com/api/v2',
+  baseUrl: 'http://localhost:3000',
   timeout: 10000,
-  // In production, this would be set via environment variables
-  apiKey: typeof window !== 'undefined' ? (window as any).__CHAINALYSIS_API_KEY__ : undefined
+  // API key is now configured only on the server side via CHAINALYSIS_API_KEY env var.
+  // The browser never has access to this key.
+  apiKey: undefined
 };
 
 // Export singleton instance
diff --git a/src/utils/security/transactionSecurity.ts b/src/utils/security/transactionSecurity.ts
index c5ce3d55..b18d1205 100644
--- a/src/utils/security/transactionSecurity.ts
+++ b/src/utils/security/transactionSecurity.ts
@@ -75,17 +75,40 @@ export function createTrustedDeviceId(): string {
   return `trusted_${crypto.randomUUID()}`;
 }
 
+function simpleHash(input: string): string {
+  let hash = 0;
+  for (let i = 0; i < input.length; i++) {
+    const char = input.charCodeAt(i);
+    hash = ((hash << 5) - hash) + char;
+    hash |= 0;
+  }
+  return Math.abs(hash).toString(16).padStart(8, '0');
+}
+
+const SESSION_SALT_KEY = 'propchain-session-salt';
+
+function getSessionSalt(): string {
+  let salt = window.sessionStorage.getItem(SESSION_SALT_KEY);
+  if (!salt) {
+    salt = crypto.randomUUID();
+    window.sessionStorage.setItem(SESSION_SALT_KEY, salt);
+  }
+  return salt;
+}
+
 export function getSecurityDeviceId(): string {
   if (typeof window === 'undefined') {
     return 'server-device';
   }
 
-  const key = 'propchain-security-device-id';
+  const key = 'propchain-security-device-id-hash';
   const existing = window.localStorage.getItem(key);
   if (existing) return existing;
 
   const deviceId = crypto.randomUUID();
-  window.localStorage.setItem(key, deviceId);
+  const salt = getSessionSalt();
+  const hashedId = simpleHash(`${deviceId}:${salt}`);
+  window.localStorage.setItem(key, hashedId);
   return deviceId;
 }