ISO/IEC 19794-7:2007
(Main)Information technology — Biometric data interchange formats — Part 7: Signature/sign time series data
Information technology — Biometric data interchange formats — Part 7: Signature/sign time series data
ISO/IEC 19794-7:2007 specifies two data interchange formats for signature/sign behavioural data captured in the form of time series using devices such as digitizing tablets or advanced pen systems. One data interchange format is for general use and the other one is a compact format for use with smart cards or other tokens. Both data interchange formats can be used for both acquired signature/sign samples (serving as a starting point for feature extraction) and for time-series features (to be compared directly by time-series based comparison algorithms). Abstract syntax notation one (ASN.1) specifications of the data interchange formats and encoding instructions are provided in an informative annex.
Technologies de l'information — Formats d'échange de données biométriques — Partie 7: Données de série chronologique de signature/signe
General Information
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Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 19794-7
First edition
2007-06-15
Information technology — Biometric data
interchange formats —
Part 7:
Signature/sign time series data
Technologies de l'information — Formats d'échange de données
biométriques —
Partie 7: Données de série chronologique de signature/signe
Reference number
ISO/IEC 19794-7:2007(E)
©
ISO/IEC 2007
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ISO/IEC 19794-7:2007(E)
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ISO/IEC 19794-7:2007(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Conformance. 1
3 Normative references . 1
4 Terms and definitions. 2
5 Conventions . 4
5.1 Coordinate system. 4
5.2 Octet order. 4
5.3 Registered format type identifiers . 4
6 Channels. 5
6.1 General. 5
6.2 Pen position channels: X, Y, Z . 5
6.3 Pen velocity channels: VX, VY . 6
6.4 Pen acceleration channels: AX, AY . 6
6.5 Time channel: T. 6
6.6 Time difference channel: DT. 6
6.7 Pen tip force channel: F . 6
6.8 Tip switch state channel: S. 6
6.9 Pen orientation channels: TX, TY, Az, El, R . 6
7 Full format . 7
7.1 Introduction . 7
7.2 BDB organisation. 7
7.3 BDB header . 7
7.4 BDB body. 11
8 Compact format . 12
8.1 Introduction . 12
8.2 Matching algorithm parameters template . 13
8.3 Embedment in a CBEFF data structure. 14
8.4 BDB body. 15
Annex A (informative) Best practices — Data acquisition. 16
Annex B (informative) ASN.1 specification of the data interchange formats . 17
Annex C (informative) Signature/sign coding examples. 21
Bibliography . 23
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ISO/IEC 19794-7:2007(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC 19794-7 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 37, Biometrics.
ISO/IEC 19794 consists of the following parts, under the general title Information technology — Biometric data
interchange formats:
⎯ Part 1: Framework
⎯ Part 2: Finger minutiae data
⎯ Part 3: Finger pattern spectral data
⎯ Part 4: Finger image data
⎯ Part 5: Face image data
⎯ Part 6: Iris image data
⎯ Part 7: Signature/sign time series data
⎯ Part 8: Finger pattern skeletal data
⎯ Part 9: Vascular image data
⎯ Part 10: Hand geometry silhouette data
The following part is under preparation:
⎯ Part 11: Signature/sign processed dynamic data
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INTERNATIONAL STANDARD ISO/IEC 19794-7:2007(E)
Information technology — Biometric data interchange
formats —
Part 7:
Signature/sign time series data
1 Scope
For the purposes of biometric verification and/or identification, this part of ISO/IEC 19794 specifies a concept
and data interchange formats for dynamic signature/sign behavioural data captured in the form of a time
series using devices such as digitizing tablets or advanced pen systems. The data interchange formats are
generic in that they may be applied and used in a wide range of application areas where handwritten signs or
signatures are involved. No application-specific requirements or features are addressed in this part of
ISO/IEC 19794. This part of ISO/IEC 19794 contains definitions of relevant terms, a description of what data is
captured, two data formats for containing the data — one for general use and one compact format for use with
smart cards and other tokens — alongside examples of data block contents and best practice in capture.
Specifying which of the format types and which options defined in this part of ISO/IEC 19794 are to be applied
in a particular application is out of the scope of this part of ISO/IEC 19794; this needs to be defined in
application-specific requirements specifications or application profiles. It is advisable that stored and
transmitted biometric data be time-stamped and that cryptographic techniques be used to protect their
authenticity, integrity and confidentiality; however such provisions are beyond the scope of this part of
ISO/IEC 19794.
2 Conformance
A biometric data block conforms to this part of ISO/IEC 19794 if it satisfies the format requirements with
respect to its structure, with respect to relations among its fields, and with respect to relations between its
fields and the underlying input that are specified within the normative clauses of this part of ISO/IEC 19794.
3 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO/IEC 19785-1, Information technology — Common Biometric Exchange Formats Framework — Part 1:
Data element specification
ISO/IEC 19785-2, Information technology — Common Biometric Exchange Formats Framework — Part 2:
Procedures for the operation of the Biometric Registration Authority
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ISO/IEC 19794-7:2007(E)
ISO/IEC 19785-3, Information technology — Common Biometric Exchange Formats Framework — Part 3:
1)
Patron format specifications
ISO/IEC 19794-1, Information technology — Biometric data interchange formats — Part 1: Framework
4 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 19794-1 and the following apply.
4.1
signature/sign
handwritten signature or handwritten personal sign
4.2
time series
sequence of values sampled at successive points in time
4.3
biometric data block
BDB
block of data with a defined format that contains one or more biometric samples or biometric templates
4.4
channel
data item (acquired, intermediate or processed) recorded in the form of a time series
NOTE Examples include pen position, pen tip force and tilt.
4.5
pen azimuth
angle measured clockwise from the positive y axis to the perpendicular projection of the pen onto the writing
plane
NOTE For an illustration, see Figure 1 (upper left and lower left).
4.6
pen elevation
angle measured counter-clockwise from the perpendicular projection of the pen onto the writing plane to the
pen
NOTE For an illustration, see Figure 1 (upper left and lower left).
4.7
pen tilt along the x axis
angle measured clockwise from the positive z axis to the perpendicular projection of the pen onto the
x,z plane
NOTE For an illustration, see Figure 1 (upper right and lower left).
4.8
pen tilt along the y axis
angle measured clockwise from the positive z axis to the perpendicular projection of the pen onto the
y,z plane
NOTE For an illustration, see Figure 1 (upper right and lower left).
1) To be published.
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ISO/IEC 19794-7:2007(E)
Figure 1 — Azimuth and elevation angles (upper left), tilt angles (upper right),
pen orientation decomposition (lower left), and pen rotation (lower right)
4.9
pen rotation
angle of rotation of the pen about its longitudinal axis measured counter-clockwise from a device-specific
reference rotational position
NOTE For an illustration, see Figure 1 (lower right).
4.10
X jitter
standard deviation of 100 x-coordinate samples from a stationary pen
4.11
Y jitter
standard deviation of 100 y-coordinate samples from a stationary pen
4.12
X resolution
number of dots per centimetre that the capture device resolves in the X (horizontal) direction
4.13
Y resolution
number of dots per centimetre that the capture device resolves in the Y (vertical) direction
4.14
Z resolution
number of dots per centimetre that the capture device resolves in the Z direction
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ISO/IEC 19794-7:2007(E)
4.15
sampling rate
rate in samples per second at which channel values are recorded
4.16
F resolution
number of units per millinewton that the capture device resolves in the downwards force of the pen tip on the
writing plane
5 Conventions
5.1 Coordinate system
The coordinate system used to express the pen position shall be a three-dimensional Cartesian coordinate
system. The x axis shall be the horizontal axis of the writing plane, with x coordinates increasing to the right.
The y axis shall be the vertical axis of the writing plane, with y coordinates increasing upwards. The z axis
shall be the axis perpendicular to the writing plane, with z coordinates increasing upwards out of the writing
plane starting from 0.
5.2 Octet order
The more significant octets of any multi-octet quantity are stored at lower addresses in memory than (and are
transmitted before) less significant octets.
Within an octet, the bits are numbered from 8 to 1, where bit 8 is the ‘most significant bit’ (MSB) and bit 1 the
‘least significant bit’ (LSB).
5.3 Registered format type identifiers
The biometric data block (BDB) specified in this part of ISO/IEC 19794 shall be embedded in a CBEFF-
compliant structure. The structure of a signature/sign time series biometric information record (BIR) is
depicted in Figure 2.
CBEFF standard biometric header
Signature/sign time series data block header
Signature/sign time series data block ´
Signature/sign time series data block body
CBEFF security block
Figure 2 — Overview of a signature/sign time series BIR
NOTE The CBEFF security block holds data that enables the integrity and/or the originator of the signature/ sign time
series BIR to be verified [(electronic signature or message authentication code (MAC)].
A CBEFF standard biometric header includes the data elements format owner and format type. Format owner
and format type shall be encoded according to ISO/IEC 19785 (CBEFF). The format owner is
ISO/IEC JTC 1/SC 37 with the IBIA registered format owner identifier 257 (0101 ).
Hex
The registrations listed in Table 1 have been made with the CBEFF Registration Authority (see
ISO/IEC 19785-2) to identify the signature/sign time series full format and the signature/sign time series
compact format.
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ISO/IEC 19794-7:2007(E)
Table 1 — Format type identifiers
CBEFF BDB format Short name Full object identifier
type identifier
14 (000e )
signature-sign- {iso(1) registration-authority(1) cbeff(19785) organizations(0) 257
Hex
time-series-full bdbs(0) signature-sign-time-series-full(14)}
15 (000f ) signature-sign- {iso(1) registration-authority(1) cbeff(19785) organizations(0) 257
Hex
time-series-compact bdbs(0) signature-sign-time-series-compact(16)}
6 Channels
6.1 General
Table 2 lists the channel names and their meanings. Signature/sign behavioural data captured with different
capture devices or used in different applications may contain data from different channels. Inclusion of the X
and Y channels is mandatory. Either the T channel or the DT channel must be present, or uniform sampling
(constant time difference between adjacent sample points) must be indicated. Inclusion of the other channels
is optional.
Table 2 — Channels
Channel name Interpretation
X x coordinate (horizontal pen position)
Y y coordinate (vertical pen position)
Z z coordinate (height of pen above the writing plane)
VX velocity in x direction
VY velocity in y direction
AX acceleration in x direction
AY acceleration in y direction
T time
DT time difference
F pen tip force (pressure)
S tip switch state (touching/not touching the writing plane)
TX tilt along the x axis
TY tilt along the y axis
Az azimuth angle of the pen (yaw)
El elevation angle of the pen (pitch)
R rotation (rotation about the pen axis)
6.2 Pen position channels: X, Y, Z
There are 3 channels defined for recording pen position data in the three-dimensional space. The horizontal
and vertical pen position in the writing plane is recorded in the X and Y channels, respectively. The height of
the pen above the writing plane is recorded in the Z channel.
The unit of measurement is metres (m). To restore the actual values, the integer values given in the BDB body
are to be divided by a scaling value given in the BDB header. By choosing appropriate scaling values,
different resolutions can be expressed for several applications.
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ISO/IEC 19794-7:2007(E)
6.3 Pen velocity channels: VX, VY
The horizontal and vertical pen velocity in the writing plane is recorded in the VX and VY channels,
respectively.
The unit of measurement is metres per second (m/s). To restore the actual values, the integer values given in
the BDB body are to be divided by a scaling value given in the BDB header. By choosing appropriate scaling
values, different resolutions can be expressed for several applications.
6.4 Pen acceleration channels: AX, AY
The horizontal and vertical pen acceleration in the writing plane is recorded in the AX and AY channels,
respectively.
2
The unit of measurement is metres per square second (m/s ). To restore the actual values, the integer values
given in the BDB body are to be divided by a scaling value given in the BDB header. By choosing appropriate
scaling values, different resolutions can be expressed for several applications.
6.5 Time channel: T
The T channel is defined for recording time data relative to the first sample.
The unit of measurement is seconds (s). To restore the actual values, the integer values given in the BDB
body are to be divided by a scaling value given in the BDB header. By choosing appropriate scaling values,
different resolutions can be expressed for several applications.
6.6 Time difference channel: DT
The DT channel is defined for recording time data relative to the previous sample.
The unit of measurement is seconds (s). To restore the actual values, the integer values given in the BDB
body are to be divided by a scaling value given in the BDB header. By choosing appropriate scaling values,
different resolutions can be expressed for several applications.
6.7 Pen tip force channel: F
The F channel is defined for recording pen forces (pressure) data.
The unit of measurement is Newton (N). To restore the actual values, the integer values given in the BDB
body are to be divided by a scaling value given in the BDB header. By choosing appropriate scaling values,
different resolutions can be expressed for several applications.
6.8 Tip switch state channel: S
The S channel is defined for recording whether the pen touches the writing plane or not. The data values shall
be 0 in case of non-touching and 1 in case of touching.
6.9 Pen orientation channels: TX, TY, Az, El, R
There are 5 channels defined for recording pen orientation data. Implementers may choose to use either
azimuth and elevation or tilt angles. The third degree of freedom in orientation is defined as the rotation of the
pen about its axis. All 5 pen orientation channels are optional.
The unit of measurement is degree (°).To restore the actual values, the integer values given in the BDB body
are to be divided by a scaling value given in the BDB header. By choosing appropriate scaling values,
different resolutions can be expressed for several applications.
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ISO/IEC 19794-7:2007(E)
7 Full format
7.1 Introduction
The signature/sign time series data full format shall be used to achieve interoperability between capture
devices used for the purposes of capturing signature/sign data for biometric verification or identification as well
as some form of interoperability between biometric systems. A signature/sign time series data block in this
format contains descriptive information about the structure and contents of the data block.
7.2 BDB organisation
The organisation of the BDB shall be as follows:
a) mandatory variable-length BDB header containing information about the overall BDB,
b) mandatory BDB body.
Figure 3 depicts a signature/sign time series data block in full format. The solid boxes indicate fields that must
be present. The dashed boxes indicate optional fields. The length of each field in bytes is indicated in
parentheses at the bottom of the corresponding box. The ellipses indicate that more fields of the same format
may follow.
BDB header BDB body
(variable) (variable)
Format identifier Version number Channel Re- Pre- Number of Sequence of Extended Extended data
descriptions served amble sample points sample points data
n length
(4) (4) (variable) (1) (1) (3) (variable) (2) (variable)
X channel Y channel R channel Sample point 1 Sample point n
Channel
description description description
inclusion
…… ……
field
(variable) (variable) (variable) (variable) (variable)
(2)
Pre- Scaling Standard X value Y value R value
amble value …… deviation ……
(1) (2) (2) (2) (2) (2)
Figure 3 — Signature/sign time series data block in full format
7.3 BDB header
7.3.1 General
The BDB header shall contain information about the overall signature/sign time series data block. The
structure of the header shall be as defined in Table 3 and in the following subclauses.
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ISO/IEC 19794-7:2007(E)
Table 3 — Signature/sign time series data block header
BDB header field Number of octets Comments
Format identifier 4 ASCII “SDI” followed by a zero octet
Version number of this 4 “ 10” followed by a zero octet for the first issue of this part of
part of ISO/IEC 19794 ISO/IEC 19794
Channel descriptions variable Sequence of technical characteristics of the present channels
Reserved 1 Initially 00
Hex
7.3.2 Format identifier
The signature/sign time series data block shall begin with the three ASCII characters “SDI” to identify the data
block as following the full format defined in this part of ISO/IEC 19794, followed by a zero octet as a string
terminator (5344 4900 ).
Hex
7.3.3 Version number of this part of ISO/IEC 19794
The version number for the version of this part of ISO/IEC 19794 used in constructing the signature/sign time
series data block shall be placed in four octets. This version number shall consist of three ASCII characters
followed by a zero octet as a string terminator. The first and second character shall represent the major
revision number and the third character will represent the minor revision number. Upon approval of this part of
ISO/IEC 19794, the version number shall be “ 10” (203130 , an ASCII space followed by an ASCII ‘1’ and
Hex
an ASCII ‘0’).
7.3.4 Channel descriptions
7.3.4.1 Channel inclusion field
The channel descriptions field shall begin with a channel inclusion field indicating the presence or absence of
channels. The channel inclusion field shall consist of 2 octets. Each bit shall correspond to a channel as
shown in Table 4. A bit value of 1 shall encode the presence of the corresponding channel; a bit value of 0
shall encode the absence of the corresponding channel.
As an example, Figure 4 shows the channel inclusion field for signature/sign data including the channels X, Y,
T, F, S, Az, El and R.
Octet 1 Octet 2
1 1 0 0 0 0 0 101 100 111
Figure 4 — Example of a channel inclusion field
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ISO/IEC 19794-7:2007(E)
Table 4 — Format of the channel inclusion field
Channel name Octet Bit position
X 1 8 (MSB)
Y 1 7
Z 1 6
VX 1 5
VY 1 4
AX 1 3
AY 1 2
T 1 1 (LSB)
DT 2 8 (MSB)
F 2 7
S 2 6
TX 2 5
TY 2 4
Az 2 3
El 2 2
R 2 1 (LSB)
7.3.4.2 Channel description preamble
The channel inclusion field shall be followed by a sequence of channel descriptions for the channels indicated
as present in the channel inclusion field. The order of the channel descriptions is determined by the order of
indicated inclusion within the channel inclusion field (Table 4) starting with the X channel. The channel
descriptions are mandatory for all channels present in the signature/sign time series data block.
Each channel description shall begin with a preamble. Each channel description preamble shall consist of
1 octet.
Each of the bits 4 through 8 of a channel description preamble shall correspond to a channel attribute as
shown in Table 5. A bit value of 1 shall encode the presence of the corresponding channel attribute; a bit
value of 0 shall encode the absence of the corresponding channel attribute.
Table 5 — Format of a channel description preamble
Channel attribute Bit position
Scaling value 8 (MSB)
Minimum possible channel value 7
Maximum possible channel value 6
Mean value of the channel values 5
Standard deviation of the channel values 4
Constant value 3
Linear component removed 2
RFU (reserved for future use) 1 (LSB)
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ISO/IEC 19794-7:2007(E)
A value of 1 for bit 3 of a channel description preamble shall indicate that the value of this channel is constant.
If bit 3 of a channel description preamble is set to 1, then this channel shall be absent in the BDB body even
though the BDB header indicates the presence of the channel. If the channel description contains a scaling
value, then the constant value of this channel shall be 1 divided by the scaling value.
NOTE Bit 3 of the DT channel description preamble can be used to indicate uniform sampling.
A value of 1 for bit 2 of a channel description preamble shall indicate that the linear component of the
regression line for this channel has been removed from this channel.
The unused trailing bit of the preamble shall have value 0 and is reserved for future use.
If any of the bits 4 through 8 of a channel description preamble are set to 1, the preamble shall be followed by
a sequence of channel attributes in the same order as indicated in the preamble starting with the scaling value.
7.3.4.3 Scaling value
If present, scaling values shall consist of 2 octets. The 5 most significant bits of the first octet shall constitute
the exponent field E, and the remaining 11 bits shall constitute the fraction field F.
The exponent field E contains an unsigned integer representing the base 2 exponent of the scaling value
biased by 16. For the exponent, signed integer values in the range from –16 to 15 are allowed. For encoding
the exponent value, 16 is to be added in order to get an unsigned value. For decoding the exponent value, 16
is to be subtracted from the contents of E.
The fraction field F contains the bit field that lies, in binary notation, to the right of the binary point of the
mantissa of the scaling value. The mantissa shall be scaled to the range 1 ≤ mantissa < 2.
The scaling value is calculated by
exponent
11
scaling value= mantissa⋅ 2 wi
...
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