> ## Documentation Index
> Fetch the complete documentation index at: https://docs.buckspay.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Function: extractCoseKey()

# Function: extractCoseKey()

> **extractCoseKey**(`authData`): `object`

Defined in: [packages/signers/src/passkey/cose.ts:106](https://github.com/bucks-pay/buckspay-sdk/blob/43ad599d2776cb5d657043c36847b3318093ccf4/packages/signers/src/passkey/cose.ts#L106)

Extract the secp256r1 (P-256) x/y from a WebAuthn attestation's authenticatorData:
rpIdHash(32) | flags(1) | signCount(4) | aaguid(16) | credIdLen(2) | credId | COSE\_Key(CBOR)
Requires the AT (attested-credential-data) flag set.

## Parameters

### authData

`Uint8Array`

## Returns

`object`

### x

> **x**: `Uint8Array`

### y

> **y**: `Uint8Array`