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Create the right image... and secure it!
"In an information system, communication and storage are two main areas in which image security plays a vital role to guard against fraud and the illegal access of images," says Emile Pepermans, Technical Director at Ovations Technologies.
Image security is a crucial part of any information system dealing with the transfer of images. In order to maintain the integrity of each individual image, several security measures must be applied.
As far as communication is concerned, Images can be intercepted while being transmitted over a network. This can happen when the image is first sent to the storage area or when it is retrieved for viewing. Images could also be illegally accessed and/or modified in the storage area.
"The main difference between attacks on communication and storage media is that in storage media the information is typically available for observation and modification over and extended period of time, whereas in a communication media, a more precise sense of timeliness is required to launch an attack," explains Pepermans.
These pose as a major threat to any business and a single attack can result in huge losses. While external attacks can be launched, internal attacks create a more serious threat as employees have much easier access to images and data on the network. Companies have to implement more stringent security steps than the usual username and password logins.
Communication security
Verification of data being transmitted over a network can be achieved by using digital certificates that identify the user workstation from which the image is being sent. In transmission, the data is "scrambled" through cryptographic techniques rendering it unreadable to any potential eavesdroppers. The necessary network security need to be enabled for further protection.
Storage security
On the storage level images are protected in various places:
Achieving image integrity
When the image is first inserted into the image storage system, a checksum value - commonly known as a hash* or message digest - is generated from the image. This value is usually 16 bytes (128 bits) long. This makes a fingerprint of the image and uniquely identifies it. Several algorithms can be used to generate a hash with the MD5 algorithm being the most popular.
When the image is retrieved, the image hash can be recomputed and compared with the original hash value. If it is different, it indicates that the image has been tampered with and can be flagged accordingly.
"To protect the hash itself from being modified, the checksum value needs to be securely transmitted," Pepermans points out. "This checksum can be encrypted using a private key and sent as a signature on the document. The receiver uses the sender's public key to decrypt the checksum value."
If an image transferred is intercepted, altered and sent on, the system will flag this as a tampered image. The interceptor simply cannot generate a fake document with the same hash value. If the image is altered in the repository, the same principle applies as the intruder won't be able to generate the same hash value for the altered image.
"Integrity techniques attach a cryptographic signature to the image that identifies the sender and also ensures that the image has not been modified in transit.
"This will insure the highest possible form of image security that can be implemented on an image storage system," says Pepermans in conclusion.
Definitions
* hash
A fixed-size result obtained by applying a mathematical function to an arbitrary amount of data. The hash is used as a unique value of fixed size representing a large amount of data. Small changes to the data result in large, unpredictable changes in the hash.
* hashing algorithm
An algorithm used to produce a hash value of some piece of data, such as a message or session key. Typical hashing algorithms include MD2, MD4, MD5, and SHA-1.
