diff --git a/lib/utils/pkcs7-padding.js b/lib/utils/pkcs7-padding.js
new file mode 100644
index 000000000..a2e52a41c
--- /dev/null
+++ b/lib/utils/pkcs7-padding.js
@@ -0,0 +1,42 @@
+// @flow
+
+import invariant from 'invariant';
+
+/**
+ * PKCS#7 padding function for `Uint8Array` data.
+ *
+ * @param {Uint8Array} data - The data to be padded.
+ * @param {number} blockSizeBytes - The block size in bytes.
+ * @returns {Uint8Array} The padded data as a new Uint8Array.
+ */
+function pkcs7pad(data: Uint8Array, blockSizeBytes: number): Uint8Array {
+  invariant(blockSizeBytes > 0, 'block size must be positive');
+  invariant(blockSizeBytes < 256, 'block size must be less than 256');
+  const padding = blockSizeBytes - (data.length % blockSizeBytes);
+  const padded = new Uint8Array(data.length + padding);
+  padded.set(data);
+  padded.fill(padding, data.length);
+  return padded;
+}
+
+/**
+ * PKCS#7 unpadding function for `Uint8Array` data.
+ *
+ * @param {Uint8Array} data - The padded data to be unpadded.
+ * @returns {Uint8Array} The unpadded data as a new Uint8Array.
+ * @throws {Error} If the padding is invalid.
+ */
+function pkcs7unpad(data: Uint8Array): Uint8Array {
+  const padding = data[data.length - 1];
+  invariant(padding > 0, 'padding must be positive');
+  invariant(data.length >= padding, 'data length must be at least padding');
+  invariant(
+    data.subarray(data.length - padding).every(x => x === padding),
+    'invalid padding',
+  );
+
+  const unpadded = data.subarray(0, data.length - padding);
+  return unpadded;
+}
+
+export { pkcs7pad, pkcs7unpad };
diff --git a/lib/utils/pkcs7-padding.test.js b/lib/utils/pkcs7-padding.test.js
new file mode 100644
index 000000000..562cdc43b
--- /dev/null
+++ b/lib/utils/pkcs7-padding.test.js
@@ -0,0 +1,89 @@
+// @flow
+
+import { pkcs7pad, pkcs7unpad } from './pkcs7-padding.js';
+
+describe('PKCS#7 Padding', () => {
+  it('should pad data to a multiple of blockSize bytes', () => {
+    const blockSize = 16;
+    const data = generateRandomData(100);
+    const expectedPadding = 16 - (data.length % blockSize);
+
+    const padded = pkcs7pad(data, blockSize);
+    expect(padded.length % 16).toBe(0);
+    expect(padded[padded.length - 1]).toBe(expectedPadding);
+  });
+
+  it('pkcs7pad should add a full block if input is multiple of blockSize bytes', () => {
+    const blockSize = 16;
+    const data = generateRandomData(16);
+    const expectedPadding = 16;
+
+    const padded = pkcs7pad(data, blockSize);
+    expect(padded.length % 16).toBe(0);
+    expect(padded[padded.length - 1]).toBe(expectedPadding);
+  });
+
+  it('pkcs7pad should fail if blockSize is out of 1-255 range', () => {
+    const data = generateRandomData(16);
+    expect(() => pkcs7pad(data, 0)).toThrow();
+    expect(() => pkcs7pad(data, 256)).toThrow();
+  });
+
+  it('pkcs7unpad should unpad data', () => {
+    // blockSize = 16
+    const inputData = generateRandomArray(10);
+    const padded = new Uint8Array([...inputData, ...[6, 6, 6, 6, 6, 6]]);
+
+    const unpadded = pkcs7unpad(padded);
+    expect(unpadded.length).toBe(10);
+    expect(unpadded).toStrictEqual(new Uint8Array(inputData));
+  });
+
+  it('pkcs7unpad should throw if the padding length is 0', () => {
+    // blockSize = 16
+    const padded = new Uint8Array([
+      ...generateRandomArray(10),
+      ...[0, 0, 0, 0, 0, 0],
+    ]);
+    expect(() => pkcs7unpad(padded)).toThrow();
+  });
+
+  it('pkcs7unpad should throw if the padding length is > blockSize', () => {
+    // blockSize = 16
+    const padded = new Uint8Array([
+      ...generateRandomArray(10),
+      ...[17, 17, 17, 17, 17, 17],
+    ]);
+    expect(() => pkcs7unpad(padded)).toThrow();
+  });
+
+  it('pkcs7unpad should throw if the padding is invalid', () => {
+    // blockSize = 16
+    const padded = new Uint8Array([
+      ...generateRandomArray(10),
+      ...[6, 1, 2, 3, 4, 6],
+    ]);
+    expect(() => pkcs7unpad(padded)).toThrow();
+  });
+
+  it('pkcs7pad and pkcs7unpad should be inverses', () => {
+    const blockSize = 16;
+    const data = generateRandomData(100);
+    const padded = pkcs7pad(data, blockSize);
+    const unpadded = pkcs7unpad(padded);
+    expect(unpadded.length).toBe(data.length);
+    expect(unpadded).toEqual(data);
+  });
+});
+
+function generateRandomData(length: number): Uint8Array {
+  const data = new Uint8Array(length);
+  for (let i = 0; i < length; i++) {
+    data[i] = Math.floor(Math.random() * 256);
+  }
+  return data;
+}
+
+function generateRandomArray(length: number): Array<number> {
+  return new Array(length).map(() => Math.floor(Math.random() * 256));
+}