A Study On The Digital Signature On Medical Images Based On The DICOM Standard

By using picture archiving and communication system (Picture Archiving and Communicati on System,PACS), various departments of hospitals, every domestic city and every medical institutions around the world can query and transfer medical images information, which make medical image information resources are fully utilized. Clinicians can compare, study and then diagose images from the same patient and different devices, they can also be consultation over the network. At the same time, taking advantage of the information PACS provides can reduce each patient's diagnostic time. On the other hand, it can also provide the patients timely and high quality of diagnosis, treatment and care. All of these make the hospitals develop to be informatization and modernization, improve diagnosis, reduce costs, enhance management and build clinical information resources. Through telemedicine people build a new connection between medical professionals and patients which ensure the patients get consultation, treatment and care from remote expert in the hospital where patients stay.After a long time of development, remote medical has been a lot of popularity and promotion. However,because the remote medicine is an emerging discipline, and it relates to many technology, such as medical, communications, Computer, also it develops comparatively late in China, so there was some problems to be solved. The application of telemedicine not only is currently subject to equipment, funding, staff and other factors, but also there are legal obstacles. that is, the electronic delivery of diagnostic report and records for authenticity is not sure, so it can'be used as a legal evidence in possible medical incidents or court proceedings. In order to ensure the authenticity, reliability of the medical imaging diagnostic reports and records, you can use digital signature technology. The signer signs the relating medical images and eletronic documents to express that he agrees with the content of the electronic document and take the responsibility for it. By a specific technology to authenticate the identity of the parties, the digital signature system can ensure that the transmission of electronic document content has not been tampered with.DICOM (digital imaging and communication of medical,) is a important standards of PACS. Most medical equipments at home and abroad, such as CT(computed tomography scanning), MR(nuclear magnetic resonance), all support this standard. DICOM part 15 "Security Profiles"extends the DICOM standard by the option to add digital signatures to all possible DICOM objects such as images, waveforms, or structured reports. Digital signatures provide a mechanism to confirm the origin of the authentication and the integrity of a DICOM object. Supplement 41 describes how the standard has to be implemented in an application. In order to prove the originality of DICOM objects in distributed environments, for example in intranets or even the internet, the manufacturers of medical imaging systems such as MRTs or CTs are working on a solution to directly sign the created images in the modality. Until new modalities supporting the new standard for signing DICOM objects like images become available, a solution is needed to support digital signatures for modalities which are currently in use.In fact, in the present hospital system, many modern medical instrument have had digital signature of the function. But the hospital still exist many old medical devices which have not this function, and they are also still in work. For telemedicine and region medicine, these devices will not be able to prove their identity, and difficult to maintain the integrity and whether it has been tampered with. Therefore it is necessary to achieve digital signature for these older devices. Specific implementation is joining such a computer between these imaging devices and workstations directly, which completes the digital signature functionality. So the computer host have two network ports, one connecting the imaging equipment, and the other connecting the doctor workstation or server. And then, images generated from a medical imaging device transfer to the host which is responsible for the digital signature. The host signs the digital signature and then transfers the processed images out from the other port. This result is that images transmitted from medical devices can all get digitally signed and prove their identity.That is to say it can prove which department the images transmitted out belong to. So, this can prevent medical dispute. This is the the objective that this article studys. For this host, the digital signature is based on the message digest of a digital signature. Its realization process is following process. First of all, The necessary tag files inside of DICOM medical image files, such as patient names, etc, is operated Hash algorithm. There RIPEMD-160 algorithm is the first choice, becauce it is the fastest Hash algorithm and free of collision. This generates MAC (message authentication code). Next, after using the private key of the RSA algorithm to encrypt the Mac, the digital signature is formed. This digital signature is embedded in the corresponding DICOM tab. Then, this DICOM medical file will be transmitted to the corresponding doctor workstation or server. In the digital signature validation process, it is the same that we operate the same corresponding tab for Hash and get the Hash value. Then using the corresponding public key of RSA algorithm decrypts the digital signature of the DICOM medical file transported.By comparing the similarities and differences of the two Hash values, we can determine whether the file was transferred from the very person.In this article, the author do the following works. Firstly, put forward the effect of signing a digital signature in medical devices in the telemedicine and region medical. Embedding a digital signature system between every device and workstation can achieve their identities. Secondly, by following requirements of the DICOM standard and its safety profile about digital signature security summary, achieve the purpose of signing the digital signatures on the medical images that transmited from medical devices.