The English version of this specification is the only normative version. Non-normative translations may also be available.
Copyright © 2013-2014 FIDO Alliance All Rights Reserved.
This document defines all the strings and constants reserved by UAF protocols. The values defined in this document are referenced by various UAF specifications.
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Type names, attribute names and element names are written as code
.
String literals are enclosed in “”, e.g. “UAF-TLV”.
In formulas we use “|” to denote byte wise concatenation operations.
UAF specific terminology used in this document is defined in [FIDOGlossary].
All diagrams, examples, notes in this specification are non-normative.
The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [RFC2119].
This section is non-normative.
This document defines the registry of UAF-specific constants that are used and referenced in various UAF specifications. It is expected that, over time, new constants will be added to this registry. For example new authentication algorithms and new types of authenticator characteristics will require new constants to be defined for use within the specifications.
This section is normative.
The USER_VERIFY
constants are flags in a bitfield represented
as a 32 bit long integer. They describe
the methods and capabilities of an UAF authenticator for locally verifying
a user. The operational details of
these methods are opaque to the server. These constants are used in the
authoritative metadata for an authenticator,
reported and queried through the UAF Discovery APIs, and used to form authenticator
policies in UAF protocol messages.
All user verification methods must be performed locally by the authenticator in order to meet FIDO privacy principles.
USER_VERIFY_PRESENCE
0x01
USER_VERIFY_FINGERPRINT
0x02
USER_VERIFY_PASSCODE
0x04
USER_VERIFY_VOICEPRINT
0x08
USER_VERIFY_FACEPRINT
0x10
USER_VERIFY_LOCATION
0x20
USER_VERIFY_EYEPRINT
0x40
USER_VERIFY_PATTERN
0x80
USER_VERIFY_HANDPRINT
0x100
USER_VERIFY_NONE
0x200
USER_VERIFY_ALL
0x400
The KEY_PROTECTION
constants are flags in a bit field
represented as a 16 bit long integer. They describe the method an
authenticator uses to protect the private key material for FIDO registrations.
Refer to [UAFAuthnrCommands] for more details on the relevance of keys and
key protection. These constants are used in the authoritative metadata for an
authenticator, reported and queried through the UAF Discovery APIs, and used to
form authenticator policies in UAF protocol messages.
When used in metadata describing an authenticator, several of these flags are exclusive of
others (i.e. can not be combined) - the certified metadata may have
at most one of the mutually exclusive bits set to 1. When used in authenticator
policy, any bit may be set to 1, e.g. to indicate that a server is
willing to accept authenticators using either KEY_PROTECTION_SOFTWARE
or
KEY_PROTECTION_HARDWARE
.
These flags must be set according to the effective security of the
keys, in order to follow the assumptions made in [FIDOSecRef]. For example, if a key
is stored in a secure element but software running on the FIDO User Device
could call a function in the secure element to export the key either in the clear or using
an arbitrary wrapping key, then the effective security is KEY_PROTECTION_SOFTWARE
and
not KEY_PROTECTION_SECURE_ELEMENT
.
KEY_PROTECTION_SOFTWARE
0x01
KEY_PROTECTION_HARDWARE
, KEY_PROTECTION_TEE
,
KEY_PROTECTION_SECURE_ELEMENT
KEY_PROTECTION_HARDWARE
0x02
KEY_PROTECTION_SOFTWARE
KEY_PROTECTION_TEE
0x04
KEY_PROTECTION_HARDWARE
.
Exclusive in authenticator metadata with
KEY_PROTECTION_SOFTWARE
, KEY_PROTECTION_SECURE_ELEMENT
KEY_PROTECTION_SECURE_ELEMENT
0x08
KEY_PROTECTION_HARDWARE
.
Exclusive in authenticator metadata with
KEY_PROTECTION_TEE
, KEY_PROTECTION_SOFTWARE
KEY_PROTECTION_REMOTE_HANDLE
0x10
KEY_PROTECTION
flags to indicate how the local key handle wrapping key and operations are protected.
Servers MAY unset this flag in authenticator policy if they are not prepared to store and return
key handles, for example, if they have a requirement to respond
indistinguishably to authentication attempts against userIDs that do and
do not exist. Refer to [UAFProtocol] for more details.The MATCHER_PROTECTION
constants are flags in a bit field
represented as a 16 bit long integer.
They describe the method an authenticator uses to protect the matcher
that performs user verification.
These constants are used in the authoritative metadata for an authenticator,
reported and queried through
the UAF Discovery APIs, and used to form authenticator policies in
UAF protocol messages. Refer to [UAFAuthnrCommands]
for more details on the matcher component.
These flags must be set according to the effective security of the
matcher, in order to follow the assumptions made in [FIDOSecRef]. For example, if a passcode based
matcher is implemented in a secure element, but the passcode is expected to be
provided as unauthenticated parameter, then the effective security
is MATCHER_PROTECTION_SOFTWARE
and
not MATCHER_PROTECTION_ON_CHIP
.
MATCHER_PROTECTION_SOFTWARE
0x01
MATCHER_PROTECTION_TEE
,
MATCHER_PROTECTION_ON_CHIP
MATCHER_PROTECTION_TEE
0x02
MATCHER_PROTECTION_SOFTWARE
,
MATCHER_PROTECTION_ON_CHIP
MATCHER_PROTECTION_ON_CHIP
0x04
MATCHER_PROTECTION_TEE
,
MATCHER_PROTECTION_SOFTWARE
The ATTACHMENT_HINT
constants are flags in a bit field
represented as a 32 bit long. They describe the method an
authenticator uses to communicate with the FIDO User Device. These constants are reported and
queried through the UAF Discovery APIs [UAFAppAPIAndTransport], and used to form Authenticator
policies in UAF protocol messages. Because the connection
state and topology of an authenticator may be transient, these values are
only hints that can be used by server-supplied policy
to guide the user experience, e.g. to prefer a device that is connected and
ready for authenticating or confirming a low-value transaction,
rather than one that is more secure but requires more user effort.
These flags are not a mandatory part of authenticator metadata and, when present, only indicate possible states that may be reported during authenticator discovery.
ATTACHMENT_HINT_INTERNAL
0x01
A device such as a smartphone may have authenticator functionality that is able to be used both locally and remotely. In such a case, the FIDO client MUST filter and exclusively report only the relevant bit during Discovery and when performing policy matching.
This flag cannot be combined with any other ATTACHMENT_HINT
flags.
ATTACHMENT_HINT_EXTERNAL
0x02
A device such as a smartphone may have authenticator functionality that is able to be used both locally and remotely. In such a case, the FIDO UAF Client MUST filter and exclusively report only the relevant bit during discovery and when performing policy matching.
ATTACHMENT_HINT_WIRED
0x04
ATTACHMENT_HINT_WIRELESS
0x08
ATTACHMENT_HINT_NFC
0x10
ATTACHMENT_HINT_WIRELESS
flag SHOULD also be set as well.ATTACHMENT_HINT_BLUETOOTH
0x20
ATTACHMENT_HINT_WIRELESS
flag SHOULD also be set.ATTACHMENT_HINT_NETWORK
0x40
ATTACHMENT_HINT_READY
0x80
Generally this should indicate that the device is immediately available to perform user verification without additional actions such as connecting the device or creating a new biometric profile enrollment, but the exact meaning may vary for different types of devices. For example, a USB authenticator may only report itself as ready when it is plugged in, or a Bluetooth authenticator when it is paired and connected, but an NFC-based authenticator may always report itself as ready.
ATTACHMENT_HINT_WIFI_DIRECT
0x100
ATTACHMENT_HINT_WIRELESS
flag SHOULD also be set.The TRANSACTION_CONFIRMATION_DISPLAY
constants are flags
in a bit field represented as a 16 bit long
integer. They describe the availability and implementation of a
transaction confirmation display capability required
for the transaction confirmation operation. These constants are
used in the authoritative metadata for an authenticator,
reported and queried through the UAF Discovery APIs, and used to
form authenticator policies in UAF protocol messages.
Refer to [UAFAuthnrCommands] for more details on the security aspects
of TransactionConfirmation Display.
TRANSACTION_CONFIRMATION_DISPLAY_ANY
0x01
TRANSACTION_CONFIRMATION_DISPLAY_PRIVILEGED_SOFTWARE
0x02
A FIDO client that is capable of providing this
capability MAY set this bit for all authenticators of type
ATTACHMENT_HINT_INTERNAL
, even if the authoritative metadata for the
authenticator does not indicate this capability.
Software based transaction confirmation displays might be implemented within the boundaries of the ASM rather than by the authenticator itself [UAFASM].
TRANSACTION_CONFIRMATION_DISPLAY_TEE
0x04
TRANSACTION_CONFIRMATION_DISPLAY_HARDWARE
0x08
TRANSACTION_CONFIRMATION_DISPLAY_REMOTE
0x10
Names of assertion schemes are strings with a length of 8 characters.
UAF TLV based assertion scheme “UAFV1TLV”
UAF_ALG
). This assertion scheme is using a compact
Tag Length Value (TLV) encoding for the KRD and SignData messages generated
by the authenticators. This is the default assertion scheme for the UAF protocol.This section is normative.
The internal structure of UAF authenticator commands is a “Tag-Length-Value” (TLV) sequence. The tag is a 2-byte unique unsigned value describing the type of field the data represents, the length is a 2-byte unsigned value indicating the size of the value in bytes, and the value is the variable-sized series of bytes which contain data for this item in the sequence.
Although 2 bytes are allotted for the tag, only the first 14 bits (values up to 0x3FFF) should be used to accommodate the limitations of some hardware platforms.
A tag that has the 14th bit (0x2000) set indicates that it is critical and a receiver must abort processing the entire message if it cannot process that tag.
A tag that has the 13th bit (0x1000) set indicates a composite tag that can be parsed by recursive descent.