What is meant by Quantum Cryptography?

The quantum mechanical effects when used for carrying out cryptography tasks are called the quantum cryptography. This technology is also used for breaking the cryptographic systems. And the quantum mechanical effects used include:
1. The quantum computation and
2. The quantum communication

Some very popular examples of uses of quantum cryptography are as follows:
1. For the secure exchange of the quantum key distribution or key
2. Use of quantum computers that used for breaking in to the systems using signature schemes such as ElGamal and RSA and public – key encryption.

The major advantage of quantum cryptography is that by using it, a number of cryptographic tasks are completed that are almost impossible to be completed through the classical communication i.e., the non – quantum effects.

Applications of Quantum Cryptography

1. Quantum key distribution:
- This is the most widely used application.
- It can be described as the use of quantum communication for establishing a key that is shared by two parties (usually referred to as ‘Alice’ and ‘bob’) without involvement of a third party (called Eve) knowing anything regarding the key, even if it eavesdrop on the communication between the two parties.
This happens as follows:
- The bits of the key are encoded by Alice as quantum data and are sent to Bob.
- Now if Eve eavesdrops, the message will be disturbed, making Alice and Bob know about it.
- Thus, we can say that this is a form of encrypted communication.
- Further, the QKD’s security is proven mathematically without restricting the eavesdropper’s abilities.
- In CKD (classical key distribution) this is not possible.
- This is commonly known as the ‘unconditional security’.
- However, the laws of quantum mechanics also apply and there is a need for Alice and Bob to authenticate each other. - It should not be possible for Eve to impersonate as Alice or Bob.
- This can lead to man – in – the – middle – attack.

2. Quantum commitment:
- This was another task that the researchers tried to achieve with the unconditional security offered by QKD.
- Quantum commitment is actually a scheme in which apart Alice can fix a certain value i.e., to commit where it cannot be changed by Alice anymore and it is ensured that Bob won’t learn anything about it, until and unless it is decided by Alice to be revealed to Bob.
- The most common use of these schemes is in the cryptographic protocols.
- Oblivious transfers can be performed by constructing an unconditionally secure protocol from a quantum channel and commitment.
- With such transfers any distributed computations can be implemented securely.

3. Bounded – and noisy – quantum – storage model (BQSM):
- This model provides a possible way for constructing quantum commitment and OTs that unconditionally secure.
- This model assumes that a known constant Q limits the amount of quantum data stored by an adversary.
- However, no limit is imposed up on the classical data.
Idea behind this model is:
- The number of quantum bits exchanged by the involving parties is more than Q.
- This amount of information cannot be stored even by a dishonest party since the memory limit of adversary if Q quantum bits.
- This will lead it to 2 options: either discard the data or measure it.
- So now the OTs can be implemented.

Cause-Effect Graphing is a black box testing - Explain?

So many testing techniques have been categorized under the black box testing and the cause effect graphing is one of them and that is what the whole article is all about.

- A directed graph created for the purpose of mapping of the set of causes to a set of effects is nothing but a cause effect graph.
- The causes mapped in the graph are merely the input to a software system or application and the effects can be thought of as the corresponding outputs.
- The right of the cause effect graph houses all the effects with their corresponding nodes and the left side shelters all the causes and along with their corresponding nodes.
- A graph representing causes and effects in such a way is said to be a typical cause effect graph.
- It may also make use of certain intermediate nodes for the representation of the relation between the input and the output using the logical operators like AND, OR etc.
- The constraints can be effectively added to the effects and causes in the graph and these represented as the labelled edges using a dashed line along with the symbol of the constraint.

Constraint Symbols for the Causes:
1. E – exclusive
2. OaOO – one and only one
3. I – at least one

- The first constraint is used to state that at any instant any two causes (say cause 1 and cause 2) cannot be true simultaneously.
- The second constraint i.e., the inclusive constraint is used to state that at least one of the two or more numbers of causes must be true.
- The third constraint “one and only one” is used to state that the only one among all the constraints can be true.

Constraints for the Effects

1. R – requires
2. M – mask

- These are the only two valid constraints for the effects.
- The first one states that if one of the causes is true, then it implies that the other one also must be true and it also states that only one of the two constraints can be true and other can be false.
- The second constraint i.e., the mask constraint states just the opposite of the first constraint i.e., if one of the effects is true, then the other must be false.

"One point to be noted here is that the mask constraint only relates to the effects rather than relating to the causes like other constraints."

The direction of the graph is represented as shown below:
Causes -> Intermediate nodes -> Effects

Normal Forms of Cause Effect Graph

The cause effect graph is always rearranged in such a way that at any point between any input and output there lays only one node. Two normal forms of the cause effect graph have been identified:

- Conjunctive normal form
- Disjunctive normal form

When is Cause Effect Graphing performed?

One of the main purposes of the cause effect graph is the generation of the reduced decision table. The cause effect graphing is performed after the following tasks have been completed:

1. All the requirements have been reviewed to check out for any ambiguity.
2. All the requirements have been reviewed for their content.
3. It has been ensured that the requirements are complete and correct.

Cause effect graphing is basically used for hardware testing, but now it has been adopted for the use in the software testing.

It takes in to consideration only the desired external behaviour of the system and therefore it has been categorized as a black box testing technique and only selects the test cases that represent a logical relation between the causes and effects for the production of the test cases.

What are different aspects of Software Engineering Institute (SEI)?

ABOUT SEI
- Software engineering institute is often abbreviated and called as SEI.
- The full name of the institute is “The Carnegie Mellon Software Engineering Institute”.
- SEI was established in the year of 1984 and has served the nation since than.
- The institute is funded by the federal government.
- SEI is a part of Carnegie Mellon University.
- The institute also serves as source of information and technologies for other organization apart from inspiring them.
- Apart from US, SEI has branches in Virginia and Germany.
- This engineering institute works in collaboration with the government organizations and defense to make effective software driven systems and improve the existing ones.
- The institute helps organizations as such to improve their software engineering standards within their project budget.
- SEI is involved with the research work for exploring effective solutions for the problems that are experienced in software engineering.
- Another purpose is the identification and coding of the solutions that are discovered.
- It struggles to a build a world of effective software intense systems and technologies.

AIM OF SEI
- SEI aims to continually improve the existing software engineering disciplines and technologies.
- It aims to achieve effective softwares within budget and of course time.
- SEI achieves all this by creating a vast community of software engineers and other professionals in the field.
- It is done with their help creating practical technologies that are feasible enough to be implemented to solve the real world problems.
- SEI seeks to improve the good effects of the software on the world.
- SEI considers excellence, impact and integrity as its guiding values.
- SEI conducts various programs in the field of:

System design
System security
Software development
Acquisition
Process management


DEFINED INITIATIVES OF SEI
SEI has some defined initiatives which are meant for improving the engineering capabilities of the software engineering society:

1. Engineering practices:
- These practices or programs are to continually improve the software engineering capabilities for predicting, controlling and analyzing all the properties of a software system.
- Tools like SEI frame work SPLP (software product line practice), SEI SMART (service migration and reuse technique) and SEI ATAM (architecture tradeoff analysis method) are used.

2. Acquisition practices:
- These practices aim to improve the acquisition practices of the organizations.

3. Management practices:
- On top of all management practices are to manage all other practices effectively.
- It is needed to manage the development process of the software systems to achieve success.
- SEI has its own capability maturity model integration (CMMI) approach which is comprised of training courses, models and appraisal methods.
- The CMMI has improved the organization’s performance incredibly.
- Another management model that the institute uses is RMM or resiliency management model.

4. SQUARE or security quality requirements engineering:
- This method has been developed to generate security requirements in order of some priority.
- Using SQUARE method security is incorporated in to the software system at early stages.
- It is particularly used for systems based on information technology.

5. Security:
- SEI is also the origination of the CERT coordination center which is well known for its computer security programs.
- The main aim of the CERT is to resist the attacks on the computer networks by means of effective measures like appropriate system management practices.
- It is implemented to curb the damage and ensure that the service link is not damaged.

6. Conferences:
- The institute organizes workshops, meetings and conferences from time to time. - Such events are to cover topics like COTS based systems (commercial off the shelf), acquisition practices, research on software processes, CMMI, network security and so on.

7. Membership program:
- This program seeks to help other organizations to join the network.