# ProtectedHeaderFields

Defined in: [packages/filecoin-encryption-envelope/src/cose/headers.ts:91](https://github.com/FilOzone/synapse-sdk/blob/9ad84d812e1dd635b76420a7d9388555a04f31b6/packages/filecoin-encryption-envelope/src/cose/headers.ts#L91)

Logical protected-header fields, independent of their CBOR encoding.

## Extended by

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

## Properties

### alg

> **alg**: [`Alg`](/reference/filoz/filecoin-encryption-envelope/namespaces/cose/type-aliases/alg/)

Defined in: [packages/filecoin-encryption-envelope/src/cose/headers.ts:92](https://github.com/FilOzone/synapse-sdk/blob/9ad84d812e1dd635b76420a7d9388555a04f31b6/packages/filecoin-encryption-envelope/src/cose/headers.ts#L92)

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### appMetadata?

> `optional` **appMetadata?**: [`Record`](https://www.typescriptlang.org/docs/handbook/utility-types.html#recordkeys-type)\<`string`, [`CborValue`](/reference/filoz/filecoin-encryption-envelope/namespaces/cose/type-aliases/cborvalue/)\>

Defined in: [packages/filecoin-encryption-envelope/src/cose/headers.ts:101](https://github.com/FilOzone/synapse-sdk/blob/9ad84d812e1dd635b76420a7d9388555a04f31b6/packages/filecoin-encryption-envelope/src/cose/headers.ts#L101)

Opaque authenticated metadata. This package carries but does not interpret it.

***

### chunkSize?

> `optional` **chunkSize?**: `number`

Defined in: [packages/filecoin-encryption-envelope/src/cose/headers.ts:97](https://github.com/FilOzone/synapse-sdk/blob/9ad84d812e1dd635b76420a7d9388555a04f31b6/packages/filecoin-encryption-envelope/src/cose/headers.ts#L97)

Plaintext bytes per chunk. Required only for the chunked scheme.

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### contentType?

> `optional` **contentType?**: `string` \| `number`

Defined in: [packages/filecoin-encryption-envelope/src/cose/headers.ts:95](https://github.com/FilOzone/synapse-sdk/blob/9ad84d812e1dd635b76420a7d9388555a04f31b6/packages/filecoin-encryption-envelope/src/cose/headers.ts#L95)

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### iv

> **iv**: [`Uint8Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array)

Defined in: [packages/filecoin-encryption-envelope/src/cose/headers.ts:94](https://github.com/FilOzone/synapse-sdk/blob/9ad84d812e1dd635b76420a7d9388555a04f31b6/packages/filecoin-encryption-envelope/src/cose/headers.ts#L94)

12-byte IV for AES-256-GCM or 7-byte base nonce for the chunked scheme.

***

### plaintextLength?

> `optional` **plaintextLength?**: `number`

Defined in: [packages/filecoin-encryption-envelope/src/cose/headers.ts:99](https://github.com/FilOzone/synapse-sdk/blob/9ad84d812e1dd635b76420a7d9388555a04f31b6/packages/filecoin-encryption-envelope/src/cose/headers.ts#L99)

Exact plaintext length, when known before encoding. Chunked scheme only.