SureSign - Frequently Asked Questions:

Section 1 - First Principles

1. How does SureSign help publishers and other image users?
2. What type of data can a SureSign watermark be applied to?
3. Can SureSign be used to monitor the distribution of copyright material?

1. Why isn't name and address information embedded into images?
2. Does SureSign noticeably degrade the quality of image reproduction?
3. Will the watermark survive 'lossy' data compression such as JPEG?
4. Does SureSign increase the volume of data?
5. Can a SureSign watermark be easily removed by a 'pirate' or a 'hacker'?

1. Does detection take long?
2. Can a watermark be detected in a digital image on a Web site?
3. Is a SureSign watermark detectable in an image when used on a different computer platform?
4. What is the operating range of SureSign detection software?
5. Can a watermark be detected in hard copy?

1. Does Signum Technologies license the SureSign technology to other developers?
2. What are the differences between encryption, watermarking and fingerprinting?
3. Can SureSign technology be applied to media other than digital images?
4. Has Signum Technologies any patent applications to cover their technology?

1. What is the Registry?
2. How much will it cost me?
3. What information is shown on the Registry?
4. How and when can I access the Registry?

1. How does SureSign help publishers and other image users?

Publishers, advertising agencies and other image users can avoid the risk of inadvertently infringing copyright by adopting the practice of applying one of the SureSign detection tools when they are uncertain about the origin or copyright status of an image file held by them. Large volume image users can automate the monitoring of images by using SureSign Server in its detect mode which generates a log file to provide data for export to an information management system.

When a watermark is detected, SureSign detector software displays (or logs) two codes: the unique registered user's code (User ID) and the image identifier (Image ID). With this information the copyright owner may be identified, located and contacted so that usage rights and reproduction fees can be negotiated in advance of publication.

It is important to note that, whether or not a watermark is detected, image users are still under obligation to get the necessary approval from the copyright owner before using the image. One aim of SureSign is to make this an easier and more automated process.

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2. What type of data can a SureSign watermark be applied to?

At the moment, SureSign software allows a watermark to be embedded into rasterised image data, e.g. continuous tone bitmapped RGB or CMYK colour and greyscale images. In its current form, SureSign is not designed for ASCII-based electronic textural material or those vector file formats that are typically found in line-art, CAD and illustration applications. However, it is planned that future products will support an ever increasing range of digital data formats, and further extensions of the SureSign technology will protect digital video and digital audio material in a similar manner.

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3. Can SureSign be used to monitor the distribution of copyright material?

SureSign technology makes it possible to examine and thus determine the source of watermarked images that have been posted on web sites, or distributed on-line or by CD-ROMs. The format of the watermark is well suited to computerised monitoring using search engines and spiders and, thus, in the future, will allow content providers to automatically audit the use of their material. The resultant data could be used to facilitate automated billing. Signum Technologies expect to offer a web search service in the near future.

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Section 2. SureSign watermarks

1. Why isn't name and address information embedded into images?

There are two main reasons why name and address information is not embedded into images:

1. There is a trade off between the amount of watermark data that can be hidden within the carrier object data and the image quality for any given volume of object data. Therefore, the alpha-numeric scheme which forms the basis of the watermark ID was chosen because it guarantees to provide many millions of unique combinations whilst remaining visually imperceptible even in very small volumes of object data. If name, address and telephone information were embedded into the object, the resulting data level may well cause quality problems since the threshold of perception would almost certainly be exceeded.
2. Embedding name, address, telephone numbers, rights information, etc. into an image means that, as well as being restricted to very large image file sizes, the information can become outdated making the image provider difficult or impossible to locate. By holding this information remotely in an up-to-date interactive database, image creators and providers can continue to be readily identified and, most importantly, contacted quickly.

2. Does SureSign noticeably degrade the quality of image reproduction?

The sophisticated structure of the watermark was specially designed to meet very stringent quality criteria regarding the reproducibility of the watermarked information and, in use, there is normally no discernible noise. Signum Technologies is familiar with the high quality standards imposed by reprographic use and, not surprisingly, the quality thresholds for SureSign are set at a particularly high level. The carefully structured SureSign watermark is also designed to not interfere with the screening used in printing processes.

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3. Will the watermark survive 'lossy' data compression such as JPEG?

In general, yes, but since data compression techniques work by discarding varying degrees of image information and, if excessive levels of compression are used, the watermark could be difficult to detect in some circumstances. However, this usually only occurs at the point at which the data becomes unusable for quality reproduction anyway.

Tests have shown that a SureSign watermark can survive compression ratios of up to 30:1.

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4. Does SureSign increase the volume of data?

Not at all. Adding a SureSign watermark only modifies the values assigned to individual pixels, resulting in no difference between the volumes of the unwatermarked source file and the watermarked one. Occasionally, users may experience a marginal file size increase when saving a watermarked image in a compressed file format such as JPEG (however, this is usually an insignificant amount).

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5. Can a SureSign watermark be easily removed by a 'pirate' or 'hacker'?

No. It is impractical to try to remove a watermark from a file, since the considerable resources and time involved would, in most cases, be excessively disproportionate to the material's commercial value. Trying to create a 'pirate' program to remove the watermark from an image would be pointless, since each image has a totally unique watermark structure.

The permutation method used in SureSign is inherently secure and provides more options than are commonly utilised in either RSA or DES coding. Hacker programs that claim to remove a watermark, usually only render the underlying watermark data more difficult to read. Once an image is watermarked it is permanently changed and the watermark may still be recovered by 'forensic' means from images modified in this way.

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Section 3. Watermark Detection

1. Does detection take long?

Detection is normally quick and simple, taking only seconds for average file sizes, but will vary according to the computer being used, the image size and whether a watermark is actually present or not. For example, a watermarked 5MB image file takes around 4 seconds to be processed by the SureSign Detector running within Adobe Photoshop on an Apple Macintosh Power Mac 8100. If there is no watermark present, the process takes about 16 seconds. The processing time is roughly proportional to image size (given that sufficient memory is allocated to the image editing application).

High volume users, such as publishers, can use the batch processing version of the software, SureSign Server, which runs unattended in the background, watermarking or detecting, optionally changing format, moving image files, and generating report logs with little or no impact on workflow.

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2. Can a watermark be detected in a digital image on a web site?

Yes. It is possible to read watermarks embedded in JPEG images published on web sites. It is also possible to read watermarks embedded in Indexed Colour images (GIFs) although it is difficult to guarantee that the watermark can be detected in all circumstances, since this depends upon the size of sample data available and whether excessive image manipulation has taken place. Nonetheless, SureSign should prove to be of immense value to those who wish to monitor the use of their images on the Internet.

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3. Is a SureSign watermark detectable in an image when used on a different computer platform?

Generally, yes. SureSign watermarks form part of the image data itself and, irrespective of the platform or operating system used, the SureSign watermarks are retained when files are converted.

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4. What is the operating range of SureSign detection software?

There are three general cases where a valid SureSign watermark may be outside the detection range of the detector tools:

1. If the size of the image is too small, the detection tools may discover the presence of a watermark but be unable to fully decode the IDs. A warning is given in this case, however. The minimum image size to ensure successful detection is around 50KB although, in practice, a watermark may be detected in as little as 30KB of image data using the latest SureSign detection tools.
2. If the image has been heavily manipulated by transformations such as distortion, rotation or re-sizing. Typically, in these cases, the watermark is still present in the data but may not be detectable. The detector is tolerant of a range of rotation and enlargement, but if the image has been manipulated outside this range, then it should be transformed back within range before the Detector will successfully recover the watermark. Signum Technologies is continuing to enhance the performance of the detection tools to cope with an ever-increasing range of transformations without the need for operator intervention to manipulate the image.
3. If image data has been substantially degraded, either by severe re-touching, or by performing a conversion such as heavy compression or excessive down-sizing which results in image data being discarded. In this case, the watermark itself may be degraded to the extent that it can no longer be fully decoded or even detected. Generally speaking, if 10% or more of the original data remains, then a SureSign watermark should be readable.

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5. Can a watermark be detected in hard copy?

Yes. It is possible to detect the watermark in scanned-in halftone printed material and other print media such as thermal dye sublimation prints in colour and monochrome. However, it is difficult to guarantee that the watermark can be detected in all circumstances because of the widely varying screen types, printing processes and materials used in print production. Having said that, this useful additional function can allow a great many users to monitor usage of their image material in print.

Generally speaking, the higher the quality of the print and the larger the print sample, the easier it is to detect a watermark in hard copy.

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Section 4. The SureSign Technology

1. Does Signum Technologies license the SureSign technology to third parties developmental integrators?

Yes. SureSign technology is very suitable for use in a wide range of photographic, video, audio and multimedia applications in diverse sectors such as digital and print publishing, entertainment, packaging, security, healthcare, cartography and electronic commerce.

Signum has ensured that its watermarking technologycan be easily integrated into all kinds of application and system software and can also be incorporated into the firmware of the growing range of hardware devices such as digital still and video cameras, for example.

For these purposes, Signum Technologies offers a special SureSign Software Development Kit (SDK) for application developers who wish to integrate SureSign watermarking functions into their applications, systems or hardware. Public and private-key versions of the SDK are available as standard for copyright communication and protection, and data validation applications . UNIX (Solaris), Mac OS and Windows95/NT operating systems are supported but Signum Technologies can provide customised versions for use with other operating systems.

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2. What are the differences between encryption, visible watermarking and invisible watermarking?

Whilst these are all security devices for digital material and the terms are frequently used interchangeably, they are nevertheless three distinctly different protection methods.

Encryption works by locking an object file with a 'key' and providing that key only to authorised users. Whilst this generally provides a high degree of active security, once an encrypted file is opened, the contents become unprotected and may then be readily edited, copied and disseminated without any further form of control.

Visible watermarking usually places a visible mark on a still or video image. These watermarks can, of course, be removed by image processing applications and, for this reason, do not offer any high degree of protection. They are, however, frequently used as a promotional tool for identifying low resolution view files (of limited commercial value) when used as part of a 'sampler' or catalogue.

Invisible watermarking, also known as fingerprinting or digital steganography, protects image data at a very deep level with watermark data interwoven into the image data itself. Unlike visible watermarking or encryption, a watermark is designed to remain in place even after the file has been opened (or unlocked), edited or copied. The watermark structure was devised to be robust and not to be visible either in print or on screen in normal use, making it a highly effective tool in both copyright protection and data integrity applications.

In copyright protection applications, watermarking and encryption are entirely complementary techniques and, used in combination, offer a sophisticated level of both active and passive protection.

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3. Can SureSign technology be applied to media other than digital images?

Yes. New products with support digital audio and digital video applications are planned. In both these cases, the watermark information will still be kept to a minimum but, since these types of data are more tolerant of embedded data, more or larger identifying fields may be incorporated into the watermark. This should permit the support of emerging industry standard identifying codes, such as Isrc, DOI, etc.

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4. Has Signum Technologies any patent applications to cover their technology?

Yes. Signum Technologies have a number of patent applications relating to watermarking (originally called fingerprinting):

1. Security codes for digital images
   Patent application: 9400971.9 Date of filing: 19th January 1994 In the name of MOR Limited (subsequently changed to Signum Technologies Limited)
2. The watermark technique
   Patent application: 9504221.2 Date of filing: 2nd March 1995 In the name of MOR Limited (subsequently changed to Signum Technologies Limited)
3. Data Integrity
   Patent application: 9513790.7 Date of filing: 3rd July 1995 In the name of HighWater Designs Limited (subsequently changed to Signum Technologies Limited)

Section 5. The Registry

1. What is the Registry?

When you licence SureSign watermarking software you will be issued with a unique identifier (User ID). This identifier is invisibly and permanently embedded into your images using our watermarking software - anyone finding this identifier (using our freeware detector software or third party programs) will be able to trace you as the owner or provider of the image by searching the Registry on Signum's Web site. This is done either automatically, using SureSign detector software in conjunction with a Web browser, or manually by entering the User ID in the appropriate field box on the Registry.

In addition to helping to locate the owner of a digital image, the Registry can also be used to identify the owner of physical material such as a print or a transparency when they are marked with a User ID. Some SureSign users have even marked their photographic equipment and personal possessions with their User IDs.

In the UK, the Visual Creators Index (VCI) operate their own registry. As SureSign watermarking software fully supports the VCI creator ID code, licensed UK SureSign users are able to use this resource free of charge.

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2. How much will it cost me?

You do not have to pay to use the Registry.

Signum Technologies normally make an annual fee to license the use of SureSign watermarking software.The cost of this depends upon the software and licence type - please refer to the SureSign product range section for licensing costs. In most cases, the public-key watermark detector software is free.

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3. What information is shown on the Registry?

When you become a registered user your Registry entry will include the following information:

• Your unique User ID that identifies you as the creator or provider of an image. You can apply this User ID to your images using any of our SureSign software (SureSign Writer plug-in or SureSign Server).
• Contact name and address details (including links to your email and URL).
• Optionally, your company logo (or other image of your choice) can be displayed on the Registry, if required.

4. How and when can I access the Registry?

Access to the Registry is available:

• From this web site 24 hours a day
• By fax on +44 (0)1993 776939

SureSign Glossary of Terms

• Data Record - A file, or part of a file, containing digital information.
• Noise - Low-level random data within a digital signal.
• Object - Visual or audio information in digital form.
• Object data - Information contained within a data record. May be a continuous tone still image, a digital video or sound clip.
• Threshold of perception - The point at which the watermark information starts to be perceived by human eye or ear.