diff --git a/packages/scanner/doc/labels/crypto.decrypt.md b/packages/scanner/doc/labels/crypto.decrypt.md
new file mode 100644
index 0000000000..456bd1af18
--- /dev/null
+++ b/packages/scanner/doc/labels/crypto.decrypt.md
@@ -0,0 +1,7 @@
+---
+name: crypto.decrypt
+rules:
+  - hard-coded-key
+---
+
+A function that performs decryption.
diff --git a/packages/scanner/doc/labels/crypto.encrypt.md b/packages/scanner/doc/labels/crypto.encrypt.md
index 547151020d..3ba15eeb62 100644
--- a/packages/scanner/doc/labels/crypto.encrypt.md
+++ b/packages/scanner/doc/labels/crypto.encrypt.md
@@ -1,6 +1,7 @@
 ---
 name: crypto.encrypt
 rules:
+  - hard-coded-key
   - unauthenticated-encryption
 ---
 
diff --git a/packages/scanner/doc/labels/crypto.set_key.md b/packages/scanner/doc/labels/crypto.set_key.md
new file mode 100644
index 0000000000..7b4b4cb6ed
--- /dev/null
+++ b/packages/scanner/doc/labels/crypto.set_key.md
@@ -0,0 +1,7 @@
+---
+name: crypto.set_key
+rules:
+  - hard-coded-key
+---
+
+A function that sets the crytographic key for encryption, decryption, or signature.
diff --git a/packages/scanner/doc/labels/string.unpack.md b/packages/scanner/doc/labels/string.unpack.md
new file mode 100644
index 0000000000..9a623158f3
--- /dev/null
+++ b/packages/scanner/doc/labels/string.unpack.md
@@ -0,0 +1,12 @@
+---
+name: string.unpack
+rules:
+  - hard-coded-key
+---
+
+Unpacks a string into binary from a printable encoding such as hex or Base64.
+
+## Examples
+
+- Ruby [String#unpack](https://ruby-doc.org/core-3.1.2/String.html#method-i-unpack)
+- Ruby [String#unpack1](https://ruby-doc.org/core-3.1.2/String.html#method-i-unpack1)
diff --git a/packages/scanner/doc/rules/hard-coded-key.md b/packages/scanner/doc/rules/hard-coded-key.md
new file mode 100644
index 0000000000..7b5b24ff1a
--- /dev/null
+++ b/packages/scanner/doc/rules/hard-coded-key.md
@@ -0,0 +1,14 @@
+---
+rule: hard-coded-key
+name: Hard coded key
+title: Hard-coded key
+references:
+  A02:2021: https://owasp.org/Top10/A02_2021-Cryptographic_Failures/
+impactDomain: Security
+labels:
+  - crypto.encrypt
+  - crypto.decrypt
+  - crypto.set_key
+  - string.unpack
+scope: root
+---
\ No newline at end of file
diff --git a/packages/scanner/src/rules/hard-coded-key/metadata.ts b/packages/scanner/src/rules/hard-coded-key/metadata.ts
new file mode 100644
index 0000000000..9835346136
--- /dev/null
+++ b/packages/scanner/src/rules/hard-coded-key/metadata.ts
@@ -0,0 +1,12 @@
+import { Metadata } from '../lib/metadata';
+
+export default {
+  title: 'Hard-coded key',
+  scope: 'root',
+  enumerateScope: true,
+  impactDomain: 'Security',
+  references: {
+    'A02:2021': 'https://owasp.org/Top10/A02_2021-Cryptographic_Failures/',
+  },
+  labels: ['crypto.encrypt', 'crypto.decrypt', 'crypto.set_key', 'string.unpack'],
+} as Metadata;
diff --git a/packages/scanner/src/rules/hard-coded-key/rule.ts b/packages/scanner/src/rules/hard-coded-key/rule.ts
new file mode 100644
index 0000000000..6e2ec1bdcc
--- /dev/null
+++ b/packages/scanner/src/rules/hard-coded-key/rule.ts
@@ -0,0 +1,44 @@
+import { Event } from '@appland/models';
+import { AppMapIndex, MatcherResult, RuleLogic } from '../../types';
+
+function matcher(event: Event, appMapIndex: AppMapIndex): MatcherResult {
+  if (!event.receiver) return;
+
+  const receiverObjectId = event.receiver.object_id;
+  const setKey = appMapIndex.appMap.events.find(
+    (evt) =>
+      evt.isCall() &&
+      evt.receiver?.object_id === receiverObjectId &&
+      evt.labels.has('crypto.set_key')
+  );
+  if (!setKey) return;
+
+  const keyObject = setKey.parameters![0];
+  if (!keyObject) return;
+
+  const keyObjectId = keyObject.object_id;
+  const obtainKey = appMapIndex.appMap.events.find(
+    (evt) =>
+      evt.isReturn() &&
+      evt !== setKey.returnEvent &&
+      !evt.codeObject.labels.has('string.unpack') &&
+      evt.returnValue?.object_id === keyObjectId
+  );
+  if (!obtainKey) {
+    return [
+      {
+        level: 'warning',
+        event,
+        message: `Cryptographic key is not obtained from a function, and may be hard-coded`,
+        participatingEvents: { 'crypto.set_key': setKey },
+      },
+    ];
+  }
+}
+
+export default function rule(): RuleLogic {
+  return {
+    matcher,
+    where: (e: Event) => e.labels.has('crypto.encrypt'),
+  };
+}
diff --git a/packages/scanner/src/sampleConfig/default.yml b/packages/scanner/src/sampleConfig/default.yml
index 97cf07ee15..01badedb72 100644
--- a/packages/scanner/src/sampleConfig/default.yml
+++ b/packages/scanner/src/sampleConfig/default.yml
@@ -3,6 +3,7 @@ checks:
   # - rule: circular-dependency
   - rule: deserialization-of-untrusted-data
   - rule: exec-of-untrusted-command
+  - rule: hard-coded-key
   - rule: http-500
   # - rule: illegal-package-dependency
   # - rule: incompatible-http-client-request
diff --git a/packages/scanner/test/scanner/hardCodedKey.spec.ts b/packages/scanner/test/scanner/hardCodedKey.spec.ts
new file mode 100644
index 0000000000..60e0cf13fa
--- /dev/null
+++ b/packages/scanner/test/scanner/hardCodedKey.spec.ts
@@ -0,0 +1,29 @@
+import Check from '../../src/check';
+import { loadRule } from '../../src/configuration/configurationProvider';
+import { scan } from '../util';
+
+describe('hard-coded key', () => {
+  it('found', async () => {
+    const rule = await loadRule('hard-coded-key');
+    const { findings } = await scan(
+      new Check(rule),
+      './ruby/fixture/tmp/appmap/minitest/Crypt_hard_coded_key.appmap.json'
+    );
+    expect(findings).toHaveLength(1);
+    const finding1 = findings[0];
+    expect(finding1.ruleId).toEqual('hard-coded-key');
+    expect(finding1.event.id).toEqual(4);
+    expect(finding1.message).toEqual(
+      `Cryptographic key is not obtained from a function, and may be hard-coded`
+    );
+    expect(finding1.relatedEvents).toHaveLength(2);
+  });
+  it('not found', async () => {
+    const rule = await loadRule('hard-coded-key');
+    const { findings } = await scan(
+      new Check(rule),
+      './ruby/fixture/tmp/appmap/minitest/Crypt_random_key.appmap.json'
+    );
+    expect(findings).toHaveLength(0);
+  });
+});