FIDO\_ASSERT\_VERIFY(3) Library Functions Manual FIDO\_ASSERT\_VERIFY(3)

# [NAME](#NAME)

`fido_assert_verify` — verifies the signature of a FIDO2 assertion statement

# [SYNOPSIS](#SYNOPSIS)

`#include <fido.h>`

`int`  
`fido_assert_verify`(`const fido_assert_t *assert`, `size_t idx`, `int cose_alg`, `const void *pk`);

# [DESCRIPTION](#DESCRIPTION)

The [`fido_assert_verify`](#fido_assert_verify)() function verifies whether the signature contained in statement index `idx` of `assert` matches the parameters of the assertion. Before using `fido_assert_verify`() in a sensitive context, the reader is strongly encouraged to make herself familiar with the FIDO2 assertion statement process as defined in the Web Authentication (webauthn) standard.

A brief description follows:

The [`fido_assert_verify`](#fido_assert_verify~2)() function verifies whether the client data hash, relying party ID, user presence and user verification attributes of `assert` have been attested by the holder of the private counterpart of the public key `pk` of COSE type `cose_alg`, where `cose_alg` is `COSE_ES256`, `COSE_ES384`, `COSE_RS256`, or `COSE_EDDSA`, and `pk` points to a `es256_pk_t`, `es384_pk_t`, `rs256_pk_t`, or `eddsa_pk_t` type accordingly.

Please note that the first statement in `assert` has an `idx` of 0.

# [RETURN VALUES](#RETURN_VALUES)

The error codes returned by `fido_assert_verify`() are defined in `<fido/err.h>`. If statement `idx` of `assert` passes verification with `pk`, then `FIDO_OK` is returned.

# [SEE ALSO](#SEE_ALSO)

[fido\_assert\_new(3)](/man/os/libfido2/fido_assert_new.3), [fido\_assert\_set\_authdata(3)](/man/os/libfido2/fido_assert_set_authdata.3)

July 15, 2022 Linux 4.19.0-gvisor

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Document: fido_assert_verify(3) from libfido2 1.17.0-r7 (Chainguard OS)
Source: https://github.com/Yubico/libfido2