ES256_PK_NEW(3)            Library Functions Manual            ES256_PK_NEW(3)

NAME
     es256_pk_new, es256_pk_free, es256_pk_from_EC_KEY,
     es256_pk_from_EVP_PKEY, es256_pk_from_ptr, es256_pk_to_EVP_PKEY - FIDO2
     COSE ES256 API

SYNOPSIS
     #include <openssl/ec.h>
     #include <fido/es256.h>

     es256_pk_t *
     es256_pk_new(void);

     void
     es256_pk_free(es256_pk_t **pkp);

     int
     es256_pk_from_EC_KEY(es256_pk_t *pk, const EC_KEY *ec);

     int
     es256_pk_from_EVP_PKEY(es256_pk_t *pk, const EVP_PKEY *pkey);

     int
     es256_pk_from_ptr(es256_pk_t *pk, const void *ptr, size_t len);

     EVP_PKEY *
     es256_pk_to_EVP_PKEY(const es256_pk_t *pk);

DESCRIPTION
     ES256 is the name given in the CBOR Object Signing and Encryption (COSE)
     RFC to ECDSA over P-256 with SHA-256.  The COSE ES256 API of libfido2 is
     an auxiliary API with routines to convert between the different ECDSA
     public key types used in libfido2 and OpenSSL.

     In libfido2, ES256 public keys are abstracted by the es256_pk_t type.

     The es256_pk_new() function returns a pointer to a newly allocated, empty
     es256_pk_t type.  If memory cannot be allocated, NULL is returned.

     The es256_pk_free() function releases the memory backing *pkp, where *pkp
     must have been previously allocated by es256_pk_new().  On return, *pkp
     is set to NULL.  Either pkp or *pkp may be NULL, in which case
     es256_pk_free() is a NOP.

     The es256_pk_from_EC_KEY() function fills pk with the contents of ec.  No
     references to ec are kept.

     The es256_pk_from_EVP_PKEY() function fills pk with the contents of pkey.
     No references to pkey are kept.

     The es256_pk_from_ptr() function fills pk with the contents of ptr, where
     ptr points to len bytes.  The ptr pointer may point to an uncompressed
     point, or to the concatenation of the x and y coordinates.  No references
     to ptr are kept.

     The es256_pk_to_EVP_PKEY() function converts pk to a newly allocated
     EVP_PKEY type with a reference count of 1.  No internal references to the
     returned pointer are kept.  If an error occurs, es256_pk_to_EVP_PKEY()
     returns NULL.

RETURN VALUES
     The es256_pk_from_EC_KEY(), es256_pk_from_EVP_PKEY(), and
     es256_pk_from_ptr() functions return FIDO_OK on success.  On error, a
     different error code defined in <fido/err.h> is returned.

SEE ALSO
     eddsa_pk_new(3), es384_pk_new(3), fido_assert_verify(3),
     fido_cred_pubkey_ptr(3), rs256_pk_new(3)

Linux 6.7.4-arch1-1              July 15, 2022             Linux 6.7.4-arch1-1