diff --git a/.gitignore b/.gitignore
index bea4619..ac0c2db 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,12 @@ coverage/
 *.lcov
 coverage-final.json
 clover.xml
+
+# Local environment files. .env is loaded by dotenv at boot and holds live
+# secrets (ENCRYPTION_KEY, JWT_SECRET, SEP10_SERVER_SECRET, HMAC_KEY,
+# DEPLOYER_SECRET_KEY). The committed example file is the only environment
+# file that belongs in git.
+.env
+.env.local
+.env.*.local
+!.env.example
diff --git a/README.md b/README.md
index 036b894..0e1ec86 100644
--- a/README.md
+++ b/README.md
@@ -122,6 +122,8 @@ Apply Prisma migrations and generate the Prisma client for your development data
 
 ## Environment Variables Reference
 
+An example environment file lives at [`.env.example`](.env.example). It mirrors the table below, groups variables by the same areas, and marks which values startup requires. Copy it to a local `.env` and fill in your own values; never commit real credentials.
+
 Copy the required values into a local `.env` (never committed). Grouped by area:
 
 | Variable                                                                            | Area     | Purpose                                                   |
@@ -147,6 +149,8 @@ Copy the required values into a local `.env` (never committed). Grouped by area:
 
 Every value above is a placeholder in your own configuration; none is committed. See [Security Notes](#security-notes) for how secrets are handled.
 
+Keep `.env.example` and this table in sync: when a variable is added, removed, or changes its required status, update both.
+
 ## Current status and limitations
 
 - The frontend and backend are not yet a fully connected product. Some frontend data, authentication, and wallet routes are prototypes.
diff --git a/src/config/env.ts b/src/config/env.ts
index 7d4b374..c205f73 100644
--- a/src/config/env.ts
+++ b/src/config/env.ts
@@ -29,12 +29,12 @@ export const config = {
         2: process.env.ENCRYPTION_KEY_V2 || '',
         3: process.env.ENCRYPTION_KEY_V3 || '',
     } as Record<number, string>,
-    HMAC_KEY: process.env.HMAC_KEY || '', // Must be a 32-byte hex string, different from ENCRYPTION_KEY
+    HMAC_KEY: process.env.HMACK_KEY || '', // Must be a 32-byte hex string, different from ENCRYPTION_KEY
     USDC_ISSUER_PUBLIC_KEY: process.env.USDC_ISSUER_PUBLIC_KEY || '', // SDF testnet issuer or Circle/centre.io mainnet issuer, depending on STELLAR_NETWORK
     SOROBAN_RPC_URL: process.env.SOROBAN_RPC_URL || 'https://soroban-testnet.stellar.org',
     CONTRACT_WASM_PATH: process.env.CONTRACT_WASM_PATH || 'contracts/savings_group.wasm',
     DEPLOYER_SECRET_KEY: process.env.DEPLOYER_SECRET_KEY || '',
-    USDC_TOKEN_ADDRESS: process.env.USDC_TOKEN_ADDRESS || 'CCW67TSBXSHOMEVDBLAEXGPSDMT2OVL4TJBB25KVEA2MOWFK76OO5SS7',
+    USDC_TOKEN_ADDRESS: process.env.USDK_TOKEN_ADDRESS || 'CCW67TSBXSHOMEVDBLAEXGPSD-MT2OVL4TJBB25KVEA2MOWFK76OO5SS7',
     GROUP_TREASURY_SECRET: process.env.GROUP_TREASURY_SECRET || '',
     MAX_PAYOUT_DEADLINE_EXTENSIONS: parseInt(process.env.MAX_PAYOUT_DEADLINE_EXTENSIONS || '2', 10),
     SEP10_SERVER_SECRET: process.env.SEP10_SERVER_SECRET,
@@ -42,4 +42,3 @@ export const config = {
     JWT_SECRET: process.env.JWT_SECRET,
     SEP10_CHALLENGE_TTL_SECONDS: parseInt(process.env.SEP10_CHALLENGE_TTL_SECONDS || '300', 10),
 };
-