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man pages section 3: Extended Library Functions, Volume 1

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Updated: Wednesday, July 27, 2022
 
 

public_key (3erl)

Name

public_key - key infrastructure.

Synopsis

Please see following description for synopsis

Description

public_key(3)              Erlang Module Definition              public_key(3)



NAME
       public_key - API module for public-key infrastructure.

DESCRIPTION
       Provides functions to handle public-key infrastructure, for details see
       public_key(6).

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' |
           'DSAPrivateKey' | 'DSAPublicKey' | 'DHParameter' |
           'SubjectPublicKeyInfo' | 'PrivateKeyInfo' |
           'CertificationRequest' | 'CertificateList' | 'ECPrivateKey' |
           'EcpkParameters'

       asn1_type() = atom()

              ASN.1 type present in the Public Key applications ASN.1 specifi-
              cations.

       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_legacy_pubkey() = {ed_pub, ed25519 | ed448, Key :: binary()}

          Warning:
              The  tagged  ed_pub  format  will  not be returned from any pub-
              lic_key functions but can be used as input, should be considered
              deprecated.


       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_legacy_privkey() =
           {ed_pri, ed25519 | ed448, Pub :: binary(), Priv :: binary()}

          Warning:
              The  tagged  ed_pri  format  will  not be returned from any pub-
              lic_key functions but can be used as input, should be considered
              deprecated.


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

              Macro names for object identifiers for EDDSA curves used by pre-
              fixing 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()]}

       ssh_file() =
           openssh_public_key | rfc4716_public_key | known_hosts |
           auth_keys

EXPORTS
       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:pub-
              lic_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 Suggested-
              Size 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/mod-
              uli. 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:pub-
              lic_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 = string()

              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_pub-
              lic_key().

       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 = string()

              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  certifi-
              cate.  This  function  must be used for encoding certificates or
              parts of certificates that are decoded/created in the  otp  for-
              mat,  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 = 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  pol-
              icy  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 veri-
                  fication process is immediately stopped. If the verify call-
                  back  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 exten-
                  sion, 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 implementa-
                  tion:

                 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 deter-
                  mined, 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

              Translates signature algorithm OID to Erlang digest  and  signa-
              ture 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 applica-
              tions 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  connect-
              ing  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:time-
                stamp()}} :
                  The validity period of the certificate.

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

                  Default extensions included in CA certificates if not other-
                  wise 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 funcion 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,  func-
                 tion()}]

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

              See RFC 6125 for detailed information about  hostname  verifica-
              tion. 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  cer-
                  tificate.  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 bool-
                  ean()) decides the outcome. If true the the  certificate  is
                  accepted  otherwise it is rejected. See "Pinning" a Certifi-
                  cate 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() | ed_legacy_privkey()
                 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.

       ssh_decode(SshBin, Type) -> Decoded

              Types:

                 SshBin = binary()
                 Type = ssh2_pubkey | OtherType | InternalType
                 OtherType = public_key | ssh_file()
                 InternalType = new_openssh
                 Decoded = Decoded_ssh2_pubkey | Decoded_OtherType
                 Decoded_ssh2_pubkey = public_key() | ed_legacy_pubkey()
                 Decoded_OtherType =
                     [{public_key() | ed_legacy_pubkey(), Attributes}]
                 Attributes = [{atom(), term()}]

          Note:
              This function is deprecated and should not be used in  new  pro-
              grams. Use ssh_file:decode/2 instead.


              Decodes  an  SSH  file-binary.  In  the  case  of known_hosts or
              auth_keys, the binary can include one or more lines of the file.
              Returns  a  list  of  public keys and their attributes, possible
              attribute values depends on the file  type  represented  by  the
              binary.

              If the Type is ssh2_pubkey, the result will be Decoded_ssh2_pub-
              key. Otherwise it will be Decoded_OtherType.

                RFC4716 attributes - see RFC 4716.:
                  {headers, [{string(), utf8_string()}]}

                auth_key attributes - see manual page for sshd.:
                  {comment, string()}{options, [string()]}{bits, integer()}  -
                  In SSH version 1 files.

                known_host attributes - see manual page for sshd.:
                  {hostnames,  [string()]}{comment, string()}{bits, integer()}
                  - In SSH version 1 files.

              Example: {ok, SshBin} = file:read_file("known_hosts").

              If Type is public_key the binary can be either an RFC4716 public
              key or an OpenSSH public key.

       ssh_encode(InData, Type) -> binary()

              Types:

                 Type = ssh2_pubkey | OtherType
                 OtherType = public_key | ssh_file()
                 InData = InData_ssh2_pubkey | OtherInData
                 InData_ssh2_pubkey = public_key() | ed_legacy_pubkey()
                 OtherInData = [{Key, Attributes}]
                 Key = public_key() | ed_legacy_pubkey()
                 Attributes = [{atom(), term()}]

          Note:
              This  function  is deprecated and should not be used in new pro-
              grams. Use ssh_file:encode/2 instead.


              Encodes a list of SSH file entries (public keys and  attributes)
              to  a  binary.  Possible attributes depend on the file type, see
              ssh_decode/2 .

              If the Type is ssh2_pubkey, the InData shall be InData_ssh2_pub-
              key. Otherwise it shall be OtherInData.

       ssh_hostkey_fingerprint(HostKey) -> string()
       ssh_hostkey_fingerprint(DigestType, HostKey) -> string()
       ssh_hostkey_fingerprint([DigestType], HostKey) -> [string()]

              Types:

                 HostKey = public_key()
                 DigestType = digest_type()

              Calculates  a  ssh fingerprint from a public host key as openssh
              does.

          Note:
              This function is deprecated and should not be used in  new  pro-
              grams.   Use  ssh:hostkey_fingerprint/1  or  ssh:hostkey_finger-
              print/2 instead.


              The algorithm in ssh_hostkey_fingerprint/1 is md5 to be compati-
              ble  with  older ssh-keygen commands. The string from the second
              variant is prepended by the algorithm name in  uppercase  as  in
              newer ssh-keygen commands.

              Examples:

               2> public_key:ssh_hostkey_fingerprint(Key).
               "f5:64:a6:c1:5a:cb:9f:0a:10:46:a2:5c:3e:2f:57:84"

               3> public_key:ssh_hostkey_fingerprint(md5,Key).
               "MD5:f5:64:a6:c1:5a:cb:9f:0a:10:46:a2:5c:3e:2f:57:84"

               4> public_key:ssh_hostkey_fingerprint(sha,Key).
               "SHA1:bSLY/C4QXLDL/Iwmhyg0PGW9UbY"

               5> public_key:ssh_hostkey_fingerprint(sha256,Key).
               "SHA256:aZGXhabfbf4oxglxltItWeHU7ub3Dc31NcNw2cMJePQ"

               6> public_key:ssh_hostkey_fingerprint([sha,sha256],Key).
               ["SHA1:bSLY/C4QXLDL/Iwmhyg0PGW9UbY",
                "SHA256:aZGXhabfbf4oxglxltItWeHU7ub3Dc31NcNw2cMJePQ"]


       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() | ed_legacy_pubkey()
                 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, respec-
              tively. This hash is used by the c_rehash  tool  to  maintain  a
              directory of symlinks to CRL files, in order to facilitate look-
              ing up a CRL by its issuer name.



Ericsson AB                    public_key 1.11.3                 public_key(3)