Merge pull request #545 from Philipp91/patch-2

    }

    /// Creates a new `PKey` containing an HMAC key.

    ///

    /// # Note

    /// To compute HMAC values, use the `sign` module.

    pub fn hmac(key: &[u8]) -> Result<PKey, ErrorStack> {

        unsafe {

            assert!(key.len() <= c_int::max_value() as usize);