(mozilla-projects-nss-reference-fc-unwrapkey)=

# FC_UnwrapKey

## [Name](#name)

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FC_UnwrapKey - unwrap a key
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## [Syntax](#syntax)

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```{code}
CK_RV FC_UnwrapKey(
  CK_SESSION_HANDLE hSession,
  CK_MECHANISM_PTR pMechanism,
  CK_OBJECT_HANDLE hUnwrappingKey,
  CK_BYTE_PTR pWrappedKey,
  CK_ULONG usWrappedKeyLen,
  CK_ATTRIBUTE_PTR pTemplate,
  CK_ULONG usAttributeCount,
  CK_OBJECT_HANDLE_PTR phKey
);
```

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## [Parameters](#parameters)

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`hSession`

: [in] session handle.

`pMechanism`

: [in] pointer to the mechanism to use.

`hUnwrappingKey`

: [in] handle of the ket to use for unwrapping.

`pWrappedKey`

: [in] pointer to the wrapped key.

`usWrappedKeyLen`

: [in] length of the wrapped key.

`pTemplate`

: [in] pointer to the list of attributes for the unwrapped key.

`usAttributeCount`

: [in] number of attributes in the template.

`phKey`

: [out] pointer to the location to receive the handle of the unwrapped key.
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## [Description](#description)

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`FC_UnwrapKey` unwraps (decrypts) a key and creates a new key opbject. If `pWrappedKey` is
NULL the length of the wrapped key is returned in `pusWrappedKeyLen` and FC_UnwrapKey may be
called again with `pWrappedKey` set to retrieve the wrapped key.

A user must log into the token (to assume the NSS User role) before calling `FC_UnwrapKey`.
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## [Return value](#return_value)

## [Examples](#examples)

## [See also](#see_also)

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- [NSC_UnwrapKey](/en-US/NSC_UnwrapKey)
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