The UK's largest police force

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The UK's largest police force, Metropolitan police service (MPS) serves more than 7 million people in an area of 620 square miles. It consists of 30000 officers and 15000 police staff including Police Community Officers.

In MPS internally, there are many departments where each department have individual police officers working. The information that resides within these departments is highly sensitive. Only authorized users should be able to view the information by using their own identities. As MPS has different departments some of the police staff works with multiple departments. So they should be provided with multiple identities to access different departments in MPS. This causes a huge burden to the MPS to maintain multiple identities and is also very time consuming and costly. Another major issue is MPS needs to keep track of who had accessed the information or system at all instants. Therefore a dedicated solution is required to maintain such a huge database of each identity. By having a dedicated solution, MPS gains control over security and also only authorized persons have access to the data. This is achieved by having a dedicated solution where each user identity is stored and is easy to change the priority levels as required. The working staff can only access to data that they are intended to do so. The main advantage of having a dedicated solution is only authenticated and authorized users can be able to access the data. The risk of exposing the data has been reduced to a large extent.


Biometric techniques are used to authenticate or verify persons which rely on anatomical and behavioural characteristics of a person. Biometric techniques provide more advantages than pins and smart cards. Password methodology can't assure the identity of an individual where as Biometric proves the identity of a person. Passwords can be forgotten or distributed with others but not in the case of biometric techniques. Biometrics has a very high variability and can be implemented such that every user had his own characteristics. So they are unpredictable when compared to passwords. Therefore the use of biometric techniques reduces the risk of exposing data for everyone who are not intended to do that and also leads to security enhancement.

Various biometric techniques are used and the most common techniques are fingerprint technology, Iris scanners, face detection methods, Retina, handprint, Signature and voice recognition. The two techniques that I describe here are Fingerprint technology and iris scanner.


This technique is the most oldest than other techniques. Fingerprints were usually matched by using eyesight. But today, fingerprint matching is done more accurately and fast using computers. Fingerprint matching is done by categorizing into two distinct methods called Verification and Recognition. Verification is the process of accepting or denying the persons claimed identity. Recognition is the process of searching the database to identify who the person is.

Fingerprint systems normally use the characteristics of the finger rather than the actual image of the finger. Ridges and valleys are used to match the fingerprints. When the finger is placed on the platen, then the ridges of the finger are in contact with the platen but the valleys are not in contact. The fingerprint system also consists of LED Light source and a CCD placed on other side of glass platen. The laser light is focused on to the glass at a certain angle and a camera is used for capturing the reflected laser light from the glass. The light that is focused on the glass and contacted by the ridges is distributed widely and randomly. The light that is focused on valleys is reflected internally. As subsequently, the image formed on the image plane is done correspondingly as ridges to dark and valleys to bright. Due to the small size of this capacitance -based solid state fingerprint sensors are highly used and are also inexpensive. An array of electrodes is embedded into the capacitance-based fingerprint sensor. The capacitance formed by the ridges is higher than those of valleys.

Fingerprint matching is used to check whether the given fingerprint matches the original or not. Fingerprint matching depends on the representation of the fingerprint if it is like image-based, ridge pattern-based and minutiae pattern-based fingerprint representation. Minutiae are defined as the specific points in the finger image. Ridge endings and ridge bifurcations are considered when minutiae template is formed. The number of minutiae and the location of each minutiae are calculated for each fingerprint. If the non-linear distortion is high, then image-based matching is too difficult to authenticate.

The matching process is generally done by the comparing the similarity between two fingerprint representations. This calculates whether or not the provided pair of representations is captured from the same finger depending upon the similarity which is above or below the threshold.

IRIS SCANNERS: Iris scanners are used for capturing the person's characteristics in the iris of the eye and are represented by using mathematical analysis that is collected. No two iris are alike and is the most accurate technique of all the biometric devices. The user should maintain a distance of 10 cm from the scanner so that to capture the iris characteristics of the eye. The advantage of Iris scanner is if a person is enrolled once into the database, it can last lifetime. Another advantage of the Iris technique is even blind persons can be enrolled and checked because matching is done by comparing the pattern but not the sight. Iris technique is the most powerful one because it is protected by cornea and cannot be damaged even after several years, where as the fingerprint technique depends on the fingerprint and can be damaged after several years of labour work which results in false rejection rate.

The basic technique of the Iris is that the image pattern is captured and is replicated as encrypted digital template of that pattern. Thus encryption provides security against identity theft. The landmark features are used to locate the characteristics of Iris. Isolation and extraction are the features provided by the landmark features by using the distinct shape of the Iris. The Iris technology may replace passports and become the most widely used technology for international travellers. They can be implemented at airports to restrict some areas where only authorized staff is allowed.


Digital identity represents people's identity with respect to digital technology to differentiate with others identity. Biological identity is based on biometric techniques such as fingerprint, Iris, Retinal scanning, Signature dynamics, Voice dynamics, and vascular pattern. Multiple digital identities are fast in performance compared to biological identity. Biological identities are more reliable than digital identities. The production of cost is high in biological identity where as it is too low in digital identities. The biometric accuracy is higher than digital identities as it is more reliable. User acceptability is high in biological identities compared to digital identity. The most important factor to be considered is security. When both are compared, biological identities provide more security than digital identity. Digital identities are prone to many virus attacks.

A digital identity always deals with two problems which are anonymous identities and partial identities. In the case of MPS, the security level is different for each department and also access levels are different. Access levels are different to different departments because of the need to protect the sensitive data from officers who are not to access. If the member accesses the crime unit, he is permitted to access all the crime records. Biological identities are more suitable to this situation as the data is accessed with only physical access rather than any passwords or ID cards. Here the passwords or ID cards should not be used because passwords may be cracked and the data can be stolen. Biological identities have more advantages than passwords. Biological identities prove his or her owns personal identity, but where as passwords can be shared with others. A password can be forgotten and is quite hard to retrieve the lost password but in biological identity this doesn't happen as it is depends on the biometrics.

Consider another case, where the police officer is not in crime department. In this case ID cards can be used as access level as there is no high sensitive data. Biometrics are used only when data is crucial and the security should be high. Thus a police officer can work in both departments with either the crime records or normal duties with allocated permissions.


Considering the situation of metropolitan police service, messages between client and server should be transmitted securely. Secure messaging involves Authentication, Encryption and also to prevent any modifications to the message.

Encryption is the process of converting plain text into cipher text. Suppose that A needs to send a message to B, and then A encrypts the plain text with a key which results in cipher text. This cipher text is sent to B who then converts back into the plain text by using the same key. In shared key encryption, both sender and receiver possess the same key and should be rather distributed before transmission of message. When sender wants to send the message to the receiver, sender just encrypts the plain text with the shared or secret key and then sends it to the receiver. Receiver decrypts the cipher text using the secret key and then reads it as plain text. Here the secret key is known to both sender and receiver.

Public key encryption involves both public-key and a private-key. Consider the context where client and server need to communicate securely. When a client wants to send the message to server, client needs to know the public-key of server. So client obtains the public key of server and then encrypts the message using the public key. This encrypted text can only be decrypted by the server as it is the only one who has the corresponding private key. So server can only decrypt the cipher text with the private key.

Public key infrastructure (PKI) is a perfect methodology to encrypt the data. PKI uses the concept of public key cryptography to encrypt the data to send data securely. The Certificate Authority (CA) is one of the components in PKI. It is an entity which issues digital certificate. A certificate is a digital document that combines the public key with the identity of the person. This certificate is digitally signed using the private key. This provides the integrity of the contents of the certificate. PKI is really difficult to break when it is deployed and operated properly. It is quite hard to know the private key to decrypt the cipher text because it is known only to the receiver. The MPS can trust the RSA algorithm as it is the hardest cryptographic technique to break. It is based on finding the factors for a large number. It is practically impossible to break RSA as it takes years to find the private key using the latest technology. Thus a new technology needs to be invented to break RSA.


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