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NAME

       public_key - API module for public-key infrastructure.

DESCRIPTION

       Provides functions to handle public-key infrastructure, for details see public_key(7).

COMMON RECORDS AND ASN.1 TYPES

   Note:
       All  records  used in this Reference Manual are generated from ASN.1 specifications and are documented in
       the User's Guide. See Public-key Records.

       Use the following include directive to get access to the records and constant macros described  here  and
       in the User's Guide:

        -include_lib("public_key/include/public_key.hrl").

DATA TYPES

       oid() = tuple()

              Object identifier, a tuple of integers as generated by the ASN.1 compiler.

       key_oid_name() =
           rsaEncryption | 'id-RSASSA-PSS' | 'id-ecPublicKey' |
           'id-Ed25519' | 'id-Ed448' | 'id-dsa'

              Macro names for key object identifiers used by prefixing with ?

       der_encoded() = binary()

       pki_asn1_type() =
           'Certificate' | 'RSAPrivateKey' | 'RSAPublicKey' |
           'SubjectPublicKeyInfo' | 'DSAPrivateKey' | 'DHParameter' |
           'PrivateKeyInfo' | 'CertificationRequest' | 'ContentInfo' |
           'CertificateList' | 'ECPrivateKey' | 'OneAsymmetricKey' |
           'EcpkParameters'

       asn1_type() = atom()

              ASN.1 type present in the Public Key applications ASN.1 specifications.

       pem_entry() =
           {pki_asn1_type(),
            der_or_encrypted_der(),
            not_encrypted | cipher_info()}

       der_or_encrypted_der() = binary()

       cipher_info() = {cipher(), cipher_info_params()}

       cipher() = string()

       salt() = binary()

       cipher_info_params() =
           salt() |
           {#'PBEParameter'{}, digest_type()} |
           #'PBES2-params'{}

              Cipher = "RC2-CBC" | "DES-CBC" | "DES-EDE3-CBC"

              Salt could be generated with crypto:strong_rand_bytes(8).

       public_key() =
           rsa_public_key() |
           rsa_pss_public_key() |
           dsa_public_key() |
           ec_public_key() |
           ed_public_key()

       rsa_public_key() = #'RSAPublicKey'{}

       dss_public_key() = integer()

       rsa_pss_public_key() =
           {rsa_pss_public_key(), #'RSASSA-PSS-params'{}}

       dsa_public_key() = {dss_public_key(), #'Dss-Parms'{}}

       ec_public_key() = {#'ECPoint'{}, ecpk_parameters_api()}

       public_key_params() =
           'NULL' |
           #'RSASSA-PSS-params'{} |
           {namedCurve, oid()} |
           #'ECParameters'{} |
           #'Dss-Parms'{}

       ecpk_parameters() =
           {ecParameters, #'ECParameters'{}} |
           {namedCurve, Oid :: tuple()}

       ecpk_parameters_api() =
           ecpk_parameters() |
           #'ECParameters'{} |
           {namedCurve, Name :: crypto:ec_named_curve()}

       public_key_info() =
           {key_oid_name(),
            rsa_public_key() | #'ECPoint'{} | dss_public_key(),
            public_key_params()}

       ed_public_key() = {#'ECPoint'{}, ed_params()}

       ed_params() = {namedCurve, ed_oid_name()}

       private_key() =
           rsa_private_key() |
           rsa_pss_private_key() |
           dsa_private_key() |
           ec_private_key() |
           ed_private_key()

       rsa_private_key() = #'RSAPrivateKey'{}

       rsa_pss_private_key() =
           {#'RSAPrivateKey'{}, #'RSASSA-PSS-params'{}}

       dsa_private_key() = #'DSAPrivateKey'{}

       ec_private_key() = #'ECPrivateKey'{}

       ed_private_key() = #'ECPrivateKey'{parameters = ed_params()}

       ed_oid_name() = 'id-Ed25519' | 'id-Ed448'

              Macro names for object identifiers for EDDSA curves used by prefixing with ?

       key_params() =
           #'DHParameter'{} |
           {namedCurve, oid()} |
           #'ECParameters'{} |
           {rsa, Size :: integer(), PubExp :: integer()}

       digest_type() =
           none | sha1 |
           crypto:rsa_digest_type() |
           crypto:dss_digest_type() |
           crypto:ecdsa_digest_type()

       issuer_name() = {rdnSequence, [[#'AttributeTypeAndValue'{}]]}

       referenceIDs() = [referenceID()]

       referenceID() =
           {uri_id | dns_id | ip | srv_id | atom() | oid(), string()} |
           {ip, inet:ip_address() | string()}

       cert_id() = {SerialNr :: integer(), issuer_name()}

       cert() = der_cert() | otp_cert()

       otp_cert() = #'OTPCertificate'{}

       der_cert() = der_encoded()

       combined_cert() =
           #cert{der = public_key:der_encoded(),
                 otp = #'OTPCertificate'{}}

       bad_cert_reason() =
           cert_expired | invalid_issuer | invalid_signature |
           name_not_permitted | missing_basic_constraint |
           invalid_key_usage |
           {revoked, crl_reason()} |
           atom()

       crl_reason() =
           unspecified | keyCompromise | cACompromise |
           affiliationChanged | superseded | cessationOfOperation |
           certificateHold | privilegeWithdrawn | aACompromise

       chain_opts() =
           #{chain_end() := [cert_opt()],
             intermediates => [[cert_opt()]]}

       chain_end() = root | peer

       cert_opt() =
           {digest, public_key:digest_type()} |
           {key, public_key:key_params() | public_key:private_key()} |
           {validity,
            {From :: erlang:timestamp(), To :: erlang:timestamp()}} |
           {extensions, [#'Extension'{}]}

       test_root_cert() =
           #{cert := der_encoded(), key := public_key:private_key()}

       test_config() =
           #{server_config := [conf_opt()],
             client_config := [conf_opt()]}

       conf_opt() =
           {cert, public_key:der_encoded()} |
           {key, public_key:private_key()} |
           {cacerts, [public_key:der_encoded()]}

EXPORTS

       cacerts_clear() -> boolean()

              Clears any loaded CA certificates, returns true if any was loaded.

       cacerts_get() -> [combined_cert()]

              Returns the trusted CA certificates if any are loaded, otherwise uses cacerts_load/0 to load them.
              The function fails if no cacerts could be loaded.

       cacerts_load() -> ok | {error, Reason :: term()}

              Loads the OS supplied trusted CA certificates.

       cacerts_load(File :: file:filename_all()) ->
                       ok | {error, Reason :: term()}

              Loads the trusted CA certificates from a file.

       compute_key(OthersECDHkey, MyECDHkey) -> SharedSecret

              Types:

                 OthersECDHkey = #'ECPoint'{}
                 MyECDHkey = #'ECPrivateKey'{}
                 SharedSecret = binary()

              Computes shared secret.

       compute_key(OthersDHkey, MyDHkey, DHparms) -> SharedSecret

              Types:

                 OthersDHkey = crypto:dh_public()
                 MyDHkey = crypto:dh_private()
                 DHparms = #'DHParameter'{}
                 SharedSecret = binary()

              Computes shared secret.

       decrypt_private(CipherText, Key) -> PlainText

       decrypt_private(CipherText, Key, Options) -> PlainText

              Types:

                 CipherText = binary()
                 Key = rsa_private_key()
                 Options = crypto:pk_encrypt_decrypt_opts()
                 PlainText = binary()

              Public-key decryption using the private key. See also crypto:private_decrypt/4

       decrypt_public(CipherText, Key) -> PlainText

       decrypt_public(CipherText, Key, Options) -> PlainText

              Types:

                 CipherText = binary()
                 Key = rsa_public_key()
                 Options = crypto:pk_encrypt_decrypt_opts()
                 PlainText = binary()

              Public-key decryption using the public key. See also crypto:public_decrypt/4

       der_decode(Asn1Type, Der) -> Entity

              Types:

                 Asn1Type = asn1_type()
                 Der = der_encoded()
                 Entity = term()

              Decodes a public-key ASN.1 DER encoded entity.

       der_encode(Asn1Type, Entity) -> Der

              Types:

                 Asn1Type = asn1_type()
                 Entity = term()
                 Der = binary()

              Encodes a public-key entity with ASN.1 DER encoding.

       dh_gex_group(MinSize, SuggestedSize, MaxSize, Groups) ->
                       {ok, {Size, Group}} | {error, term()}

              Types:

                 MinSize = SuggestedSize = MaxSize = integer() >= 1
                 Groups = undefined | [{Size, [Group]}]
                 Size = integer() >= 1
                 Group = {G, P}
                 G = P = integer() >= 1

              Selects  a  group for Diffie-Hellman key exchange with the key size in the range MinSize...MaxSize
              and as close to SuggestedSize as possible. If Groups == undefined a  default  set  will  be  used,
              otherwise the group is selected from Groups.

              First  a  size,  as  close as possible to SuggestedSize, is selected. Then one group with that key
              size is randomly selected from the specified set of groups.  If  no  size  within  the  limits  of
              MinSize and MaxSize is available, {error,no_group_found} is returned.

              The  default  set  of groups is listed in lib/public_key/priv/moduli. This file may be regenerated
              like this:

                   $> cd $ERL_TOP/lib/public_key/priv/
                   $> generate
                       ---- wait until all background jobs has finished. It may take several days !
                   $> cat moduli-* > moduli
                   $> cd ..; make

       encrypt_private(PlainText, Key) -> CipherText

       encrypt_private(PlainText, Key, Options) -> CipherText

              Types:

                 PlainText = binary()
                 Key = rsa_private_key()
                 Options = crypto:pk_encrypt_decrypt_opts()
                 CipherText = binary()

              Public-key encryption using the private key. See also crypto:private_encrypt/4.

       encrypt_public(PlainText, Key) -> CipherText

       encrypt_public(PlainText, Key, Options) -> CipherText

              Types:

                 PlainText = binary()
                 Key = rsa_public_key()
                 Options = crypto:pk_encrypt_decrypt_opts()
                 CipherText = binary()

              Public-key encryption using the public key. See also crypto:public_encrypt/4.

       generate_key(Params :: DHparams | ECparams | RSAparams) ->
                       DHkeys | ECkey | RSAkey

              Types:

                 DHparams = #'DHParameter'{}
                 DHkeys = {PublicDH :: binary(), PrivateDH :: binary()}
                 ECparams = ecpk_parameters_api()
                 ECkey = #'ECPrivateKey'{}
                 RSAparams = {rsa, Size, PubExp}
                 Size = PubExp = integer() >= 1
                 RSAkey = #'RSAPrivateKey'{}

              Generates a new key pair. Note that except for Diffie-Hellman the public key is  included  in  the
              private key structure. See also crypto:generate_key/2

       pem_decode(PemBin :: binary()) -> [pem_entry()]

              Decodes PEM binary data and returns entries as ASN.1 DER encoded entities.

              Example {ok, PemBin} = file:read_file("cert.pem"). PemEntries = public_key:pem_decode(PemBin).

       pem_encode(PemEntries :: [pem_entry()]) -> binary()

              Creates a PEM binary.

       pem_entry_decode(PemEntry) -> term()

       pem_entry_decode(PemEntry, Password) -> term()

              Types:

                 PemEntry = pem_entry()
                 Password = iodata() | fun(() -> iodata())

              Decodes  a  PEM entry. pem_decode/1 returns a list of PEM entries. Notice that if the PEM entry is
              of type 'SubjectPublickeyInfo', it is further decoded to an rsa_public_key() or dsa_public_key().

              Password can be either an octet string or function which returns same type.

       pem_entry_encode(Asn1Type, Entity) -> pem_entry()

       pem_entry_encode(Asn1Type, Entity, InfoPwd) -> pem_entry()

              Types:

                 Asn1Type = pki_asn1_type()
                 Entity = term()
                 InfoPwd = {CipherInfo, Password}
                 CipherInfo = cipher_info()
                 Password = iodata()

              Creates a PEM entry that can be feed to pem_encode/1.

              If Asn1Type is 'SubjectPublicKeyInfo', Entity must be either an rsa_public_key(), dsa_public_key()
              or an ec_public_key() and this function creates the appropriate 'SubjectPublicKeyInfo' entry.

       pkix_decode_cert(Cert, Type) -> #'Certificate'{} | otp_cert()

              Types:

                 Cert = der_cert()
                 Type = plain | otp

              Decodes an ASN.1 DER-encoded PKIX certificate. Option otp uses the customized ASN.1  specification
              OTP-PKIX.asn1 for decoding and also recursively decode most of the standard parts.

       pkix_encode(Asn1Type, Entity, Type) -> Der

              Types:

                 Asn1Type = asn1_type()
                 Entity = term()
                 Type = otp | plain
                 Der = der_encoded()

              DER  encodes a PKIX x509 certificate or part of such a certificate. This function must be used for
              encoding certificates or parts of certificates that are decoded/created in the otp format, whereas
              for the plain format this function directly calls der_encode/2.

          Note:
              Subtle ASN-1 encoding errors in certificates may be worked around when decoding, this may have the
              affect that the encoding a certificate back to DER may generate different bytes then the  supplied
              original.

       pkix_is_issuer(CertorCRL, IssuerCert) -> boolean()

              Types:

                 CertorCRL = cert() | #'CertificateList'{}
                 IssuerCert = cert()

              Checks if IssuerCert issued Cert.

       pkix_is_fixed_dh_cert(Cert) -> boolean()

              Types:

                 Cert = cert()

              Checks if a certificate is a fixed Diffie-Hellman certificate.

       pkix_is_self_signed(Cert) -> boolean()

              Types:

                 Cert = cert()

              Checks if a certificate is self-signed.

       pkix_issuer_id(Cert, IssuedBy) ->
                         {ok, ID :: cert_id()} | {error, Reason}

              Types:

                 Cert = cert()
                 IssuedBy = self | other
                 Reason = term()

              Returns the x509 certificate issuer id, if it can be determined.

       pkix_normalize_name(Issuer) -> Normalized

              Types:

                 Issuer = issuer_name() | der_encoded()
                 Normalized = issuer_name()

              Normalizes an issuer name so that it can be easily compared to another issuer name.

       pkix_path_validation(Cert, CertChain, Options) ->
                               {ok, {PublicKeyInfo, PolicyTree}} |
                               {error,
                                {bad_cert, Reason :: bad_cert_reason()}}

              Types:

                 Cert = cert() | atom()
                 CertChain = [cert() | combined_cert()]
                 Options =
                     [{max_path_length, integer()} |
                      {verify_fun, {function(), term()}}]
                 PublicKeyInfo = public_key_info()
                 PolicyTree = list()

              Performs a basic path validation according to RFC 5280. However, CRL validation is done separately
              by  pkix_crls_validate/3   and  is  to be called from the supplied verify_fun. The optional policy
              tree check is currently not implemented but an empty place holder list is returned instead.

              Available options:

                {verify_fun, {fun(), InitialUserState::term()}:
                  The fun must be defined as:

                fun(OtpCert :: #'OTPCertificate'{},
                    Event :: {bad_cert, Reason :: atom() | {revoked, atom()}} |
                             {extension, #'Extension'{}},
                    InitialUserState :: term()) ->
                     {valid, UserState :: term()} |
                     {valid_peer, UserState :: term()} |
                     {fail, Reason :: term()} |
                     {unknown, UserState :: term()}.

                  If the verify callback fun returns {fail, Reason}, the  verification  process  is  immediately
                  stopped.  If  the  verify callback fun returns {valid, UserState}, the verification process is
                  continued.  This  can  be  used  to  accept  specific  path   validation   errors,   such   as
                  selfsigned_peer,  as  well  as  verifying  application-specific  extensions. If called with an
                  extension unknown to the user application, the return value  {unknown,  UserState}  is  to  be
                  used.

            Warning:
                Note  that  user  defined  custom  verify_fun  may  alter  original  path  validation error (e.g
                selfsigned_peer). Use with caution.

                {max_path_length, integer()}:
                   The max_path_length is the maximum number of non-self-issued intermediate  certificates  that
                  can  follow  the  peer certificate in a valid certification path. So, if max_path_length is 0,
                  the PEER must be signed by the trusted ROOT-CA directly, if it is 1, the path can be PEER, CA,
                  ROOT-CA, if it is 2, the path can be PEER, CA, CA, ROOT-CA, and so on.

              Explanations of reasons for a bad certificate:

                cert_expired:
                  Certificate is no longer valid as its expiration date has passed.

                invalid_issuer:
                  Certificate issuer name does not match the name of the issuer certificate in the chain.

                invalid_signature:
                  Certificate was not signed by its issuer certificate in the chain.

                name_not_permitted:
                  Invalid Subject Alternative Name extension.

                missing_basic_constraint:
                  Certificate, required to  have  the  basic  constraints  extension,  does  not  have  a  basic
                  constraints extension.

                invalid_key_usage:
                  Certificate key is used in an invalid way according to the key-usage extension.

                {revoked, crl_reason()}:
                  Certificate has been revoked.

                atom():
                  Application-specific error reason that is to be checked by the verify_fun.

       pkix_crl_issuer(CRL) -> Issuer

              Types:

                 CRL = der_encoded() | #'CertificateList'{}
                 Issuer = issuer_name()

              Returns the issuer of the CRL.

       pkix_crls_validate(OTPcertificate, DPandCRLs, Options) ->
                             CRLstatus

              Types:

                 OTPcertificate = #'OTPCertificate'{}
                 DPandCRLs = [DPandCRL]
                 DPandCRL = {DP, {DerCRL, CRL}}
                 DP = #'DistributionPoint'{}
                 DerCRL = der_encoded()
                 CRL = #'CertificateList'{}
                 Options = [{atom(), term()}]
                 CRLstatus = valid | {bad_cert, BadCertReason}
                 BadCertReason =
                     revocation_status_undetermined |
                     {revocation_status_undetermined, Reason :: term()} |
                     {revoked, crl_reason()}

              Performs   CRL   validation.   It   is   intended   to   be   called   from   the  verify  fun  of
              pkix_path_validation/3 .

              Available options:

                {update_crl, fun()}:
                  The fun has the following type specification:

                 fun(#'DistributionPoint'{}, #'CertificateList'{}) ->
                        #'CertificateList'{}

                  The fun uses the information in the distribution point to access the latest  possible  version
                  of the CRL. If this fun is not specified, Public Key uses the default implementation:

                 fun(_DP, CRL) -> CRL end

                {issuer_fun, fun()}:
                  The fun has the following type specification:

                fun(#'DistributionPoint'{}, #'CertificateList'{},
                    {rdnSequence,[#'AttributeTypeAndValue'{}]}, term()) ->
                     {ok, #'OTPCertificate'{}, [der_encoded]}

                  The fun returns the root certificate and certificate chain that has signed the CRL.

                 fun(DP, CRL, Issuer, UserState) -> {ok, RootCert, CertChain}

                {undetermined_details, boolean()}:
                  Defaults  to  false.  When  revocation  status cannot be determined, and this option is set to
                  true, details of why no CRLs where accepted are included in the return value.

       pkix_crl_verify(CRL, Cert) -> boolean()

              Types:

                 CRL = der_encoded() | #'CertificateList'{}
                 Cert = cert()

              Verify that Cert is the CRL signer.

       pkix_dist_point(Cert) -> DistPoint

              Types:

                 Cert = cert()
                 DistPoint = #'DistributionPoint'{}

              Creates a distribution point for CRLs issued by the same issuer as Cert. Can be used as  input  to
              pkix_crls_validate/3

       pkix_dist_points(Cert) -> DistPoints

              Types:

                 Cert = cert()
                 DistPoints = [#'DistributionPoint'{}]

              Extracts distribution points from the certificates extensions.

       pkix_hash_type(HashOid :: oid()) ->
                         DigestType ::
                             md5 | crypto:sha1() | crypto:sha2()

              Translates OID to Erlang digest type

       pkix_match_dist_point(CRL, DistPoint) -> boolean()

              Types:

                 CRL = der_encoded() | #'CertificateList'{}
                 DistPoint = #'DistributionPoint'{}

              Checks  whether the given distribution point matches the Issuing Distribution Point of the CRL, as
              described in RFC 5280. If the CRL doesn't  have  an  Issuing  Distribution  Point  extension,  the
              distribution point always matches.

       pkix_sign(Cert, Key) -> Der

              Types:

                 Cert = #'OTPTBSCertificate'{}
                 Key = private_key()
                 Der = der_encoded()

              Signs an 'OTPTBSCertificate'. Returns the corresponding DER-encoded certificate.

       pkix_sign_types(AlgorithmId) -> {DigestType, SignatureType}

              Types:

                 AlgorithmId = oid()
                 DigestType = crypto:rsa_digest_type() | none
                 SignatureType = rsa | dsa | ecdsa | eddsa

              Translates signature algorithm OID to Erlang digest and signature types.

              The AlgorithmId is the signature OID from a certificate or a certificate revocation list.

       pkix_test_data(ChainConf) -> TestConf

              Types:

                 ChainConf =
                     #{server_chain := chain_opts(), client_chain := chain_opts()} |
                     chain_opts()
                 TestConf = test_config() | [conf_opt()]

              Creates  certificate  configuration(s)  consisting  of  certificate  and  its  private key plus CA
              certificate bundle, for a client and  a  server,  intended  to  facilitate  automated  testing  of
              applications  using  X509-certificates,  often through SSL/TLS. The test data can be used when you
              have control over both the client and the server in a test scenario.

              When this function is called with a map containing client  and  server  chain  specifications;  it
              generates  both  a client and a server certificate chain where the cacerts returned for the server
              contains the root cert the server should trust and the intermediate certificates the server should
              present to connecting clients. The root cert the server should trust is the one used  as  root  of
              the  client certificate chain. Vice versa applies to the cacerts returned for the client. The root
              cert(s) can either be pre-generated with  pkix_test_root_cert/2 , or if options are specified;  it
              is (they are) generated.

              When this function is called with a list of certificate options; it generates a configuration with
              just  one  node  certificate  where cacerts contains the root cert and the intermediate certs that
              should be presented to a peer. In this case the same root cert must be used for all peers. This is
              useful in for example an Erlang distributed cluster where any node,  towards  another  node,  acts
              either  as  a  server  or as a client depending on who connects to whom. The generated certificate
              contains a subject altname, which is not needed in a client certificate, but makes the certificate
              useful for both roles.

              Explanation of the options used to customize certificates in the generated chains:

                  {digest, digest_type()}: Hash algorithm to be used for signing the certificate  together  with
                  the key option. Defaults to sha that is sha1.

                  {key,  key_params() | private_key()}: Parameters to be used to call public_key:generate_key/1,
                  to generate a key, or an existing key. Defaults to generating an ECDSA key.  Note  this  could
                  fail if Erlang/OTP is compiled with a very old cryptolib.

                  {validity,  {From::erlang:timestamp(),  To::erlang:timestamp()}}  : The validity period of the
                  certificate.

                  {extensions, [#'Extension'{}]}: Extensions to include in the certificate.

                  Default extensions included in CA certificates if not otherwise specified are:

                [#'Extension'{extnID = ?'id-ce-keyUsage',
                              extnValue = [keyCertSign, cRLSign],
                              critical = false},
                #'Extension'{extnID = ?'id-ce-basicConstraints',
                             extnValue = #'BasicConstraints'{cA = true},
                             critical = true}]

                  Default extensions included in the server peer cert if not otherwise specified are:

                [#'Extension'{extnID = ?'id-ce-keyUsage',
                              extnValue = [digitalSignature, keyAgreement],
                              critical = false},
                #'Extension'{extnID = ?'id-ce-subjectAltName',
                             extnValue = [{dNSName, Hostname}],
                             critical = false}]

                  Hostname is the result of calling net_adm:localhost() in the Erlang node where  this  function
                  is called.

          Note:
              Note that the generated certificates and keys does not provide a formally correct PKIX-trust-chain
              and  they  cannot be used to achieve real security. This function is provided for testing purposes
              only.

       pkix_test_root_cert(Name, Options) -> RootCert

              Types:

                 Name = string()
                 Options = [cert_opt()]
                 RootCert = test_root_cert()

              Generates a root certificate that can be used in multiple calls to pkix_test_data/1 when you  want
              the same root certificate for several generated certificates.

       pkix_subject_id(Cert) -> ID

              Types:

                 Cert = cert()
                 ID = cert_id()

              Returns the X509 certificate subject id.

       pkix_verify(Cert, Key) -> boolean()

              Types:

                 Cert = der_cert()
                 Key = public_key()

              Verifies PKIX x.509 certificate signature.

       pkix_verify_hostname(Cert, ReferenceIDs) -> boolean()

       pkix_verify_hostname(Cert, ReferenceIDs, Options) -> boolean()

              Types:

                 Cert = cert()
                 ReferenceIDs = referenceIDs()
                 Options = [{match_fun | fail_callback | fqdn_fun, function()}]

              This  function  checks  that  the Presented Identifier  (e.g hostname) in a peer certificate is in
              agreement with at least one of the Reference Identifier  that the client expects to  be  connected
              to.  The  function  is  intended to be added as an extra client check of the peer certificate when
              performing public_key:pkix_path_validation/3

              See RFC 6125 for detailed information about hostname  verification.  The  User's  Guide  and  code
              examples describes this function more detailed.

              The option funs are described here:

                match_fun:

                fun(ReferenceId::ReferenceId() | FQDN::string(),
                    PresentedId::{dNSName,string()} | {uniformResourceIdentifier,string() |
                                 {iPAddress,list(byte())} | {OtherId::atom()|oid(),term()}})

                fun(....) -> true;   % My special case
                   (_, _) -> default % all others falls back to the inherit tests
                end

                See  pkix_verify_hostname_match_fun/1  for a function that takes a protocol name as argument and
                returns a fun/2 suitable for this option and Re-defining the match operation in the User's Guide
                for an example.

            Note:
                Reference Id values given as binaries will be converted to strings, and  ip  references  may  be
                given  in  string  format  that  is  "10.0.1.1"  or  "1234::5678:9012"  as well as on the format
                inet:ip_address()

                fail_callback:
                  If a matching fails, there could be circumstances when  the  certificate  should  be  accepted
                  anyway. Think for example of a web browser where you choose to accept an outdated certificate.
                  This  option  enables  implementation  of  such  an exception but for hostnames. This fun/1 is
                  called when no ReferenceID matches. The return value of the  fun  (a  boolean())  decides  the
                  outcome.  If  true  the  the certificate is accepted otherwise it is rejected. See "Pinning" a
                  Certificate in the User's Guide.

                fqdn_fun:
                  This option augments the host name extraction from URIs and other Reference IDs. It could  for
                  example  be  a  very  special  URI  that  is not standardised. The fun takes a Reference ID as
                  argument and returns one of:

                  * the hostname

                  * the atom default: the default host name extract function will be used

                  * the atom undefined: a host name could not  be  extracted.  The  pkix_verify_hostname/3  will
                    return false.

                For an example, see Hostname extraction in the User's Guide.

       pkix_verify_hostname_match_fun(Protocol) -> Result

              Types:

                 Protocol = https
                 Result = function()

              The  return  value  of  calling  this  function  is intended to be used in the match_fun option in
              pkix_verify_hostname/3.

              The returned fun augments the verify hostname matching according to the  specific  rules  for  the
              protocol in the argument.

          Note:
              Currently  supported  https  fun will allow wildcard certificate matching as specified by the HTTP
              standard. Note that for instance LDAP have a different set of wildcard matching rules. If  you  do
              not  want  to  allow  wildcard certificates (recommended from a security perspective) or otherwise
              customize the hostname  match  the  default  match  function  used  by  ssl  application  will  be
              sufficient.

       sign(Msg, DigestType, Key) -> Signature

       sign(Msg, DigestType, Key, Options) -> Signature

              Types:

                 Msg = binary() | {digest, binary()}
                 DigestType = digest_type()
                 Key = private_key()
                 Options = crypto:pk_sign_verify_opts()
                 Signature = binary()

              Creates a digital signature.

              The  Msg  is  either the binary "plain text" data to be signed or it is the hashed value of "plain
              text", that is, the digest.

       verify(Msg, DigestType, Signature, Key) -> boolean()

       verify(Msg, DigestType, Signature, Key, Options) -> boolean()

              Types:

                 Msg = binary() | {digest, binary()}
                 DigestType = digest_type()
                 Signature = binary()
                 Key = public_key()
                 Options = crypto:pk_sign_verify_opts()

              Verifies a digital signature.

              The Msg is either the binary "plain text" data or it is the hashed value of "plain text", that is,
              the digest.

       short_name_hash(Name) -> string()

              Types:

                 Name = issuer_name()

              Generates a short hash of an issuer name. The hash  is  returned  as  a  string  containing  eight
              hexadecimal digits.

              The  return value of this function is the same as the result of the commands openssl crl -hash and
              openssl x509 -issuer_hash, when passed the issuer name of a CRL or  a  certificate,  respectively.
              This  hash is used by the c_rehash tool to maintain a directory of symlinks to CRL files, in order
              to facilitate looking up a CRL by its issuer name.

Ericsson AB                                    public_key 1.13.3.2                              public_key(3erl)