# decodeProtectedHeader

> **decodeProtectedHeader**(`bytes`, `unprotectedMap?`): [`DecodedProtectedHeader`](/reference/filoz/filecoin-encryption-envelope/namespaces/cose/interfaces/decodedprotectedheader/)

Defined in: [packages/filecoin-encryption-envelope/src/cose/headers.ts:922](https://github.com/FilOzone/synapse-sdk/blob/9ad84d812e1dd635b76420a7d9388555a04f31b6/packages/filecoin-encryption-envelope/src/cose/headers.ts#L922)

Decode a protected header from its exact wire bytes and preserve those bytes
in [DecodedProtectedHeader](/reference/filoz/filecoin-encryption-envelope/namespaces/cose/interfaces/decodedprotectedheader/).

When provided, `unprotectedMap` is used to reject labels duplicated across
the protected and unprotected buckets.

## Parameters

| Parameter | Type |
| ------ | ------ |
| `bytes` | [`Uint8Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array) |
| `unprotectedMap?` | [`Map`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Map)\<[`CborValue`](/reference/filoz/filecoin-encryption-envelope/namespaces/cose/type-aliases/cborvalue/), [`CborValue`](/reference/filoz/filecoin-encryption-envelope/namespaces/cose/type-aliases/cborvalue/)\> |

## Returns

[`DecodedProtectedHeader`](/reference/filoz/filecoin-encryption-envelope/namespaces/cose/interfaces/decodedprotectedheader/)