Security attacks are classified as either passive or aggressive.

Authentication protocols and encryption algorithms are examples of security mechanisms.

The more critical a component or service, the higher the level of required availability.

Security services include access control, data confidentiality and data integrity, but do not include authentication.

The field of network and Internet security consists of measures to deter, prevent, detect and correct security violations that involve the transmission of information.

Patient allergy information is an example of an asset with a high requirement for integrity.

The OSI security architecture was not developed as an international standard, therefore causing an obstacle for computer and communication vendors when developing security features.

Data origin authentication does not provide protection against the modification of data units.

The emphasis in dealing with active attacks is on prevention rather than detection.

Symmetric encryption is used to conceal the contents of blocks or streams of data of any size, including messages, files, encryption keys, and passwords.

                    is the most common method used to conceal small blocks of data, such as encryption keys and hash function values, which are used in digital signatures.

                    is the most common method used to conceal small blocks of data, such as encryption keys and hash function values, which are used in digital signatures.

A common technique for masking contents of messages or other information traffic so that opponents can not extract the information from the message is

                    .

                    involves the passive capture of a data unit and its subsequent retransmission to produce an unauthorized effect.

The three concepts that form what is often referred to as the CIA triad are

                . These three concepts embody the fundamental security objectives for both data and for information and computing services.

Finite fields play a crucial role in several areas of cryptography.

The scheme where you can find the greatest common divisor of

two integers by repetitive application of the division algorithm is

known as the Brady algorithm.

Two integers a and b are said to be congruent modulo n, if

(a mod n) = (b mod n).

Cryptographic algorithms do not rely on properties of finite fields.

Finite fields of order p can be defined using arithmetic mod p.

The greatest common divisor of two integers is the largest positive integer that

exactly _________ both integers.

Two integers are __________ if their only common positive integer factor is 1.

The __________ of two numbers is the largest integer that divides both numbers.

A ring is said to be _________ if it satisfies the condition ab = ba for all a, b in R.

A _________ is a set of elements on which two arithmetic operations have been

defined and which has the properties of ordinary arithmetic, such as closure,

associativity, commutativity, distributivity, and having both additive and

multiplicative inverses.

Unlike ordinary addition, there is not an additive inverse to each

integer in modular arithmetic.

If b|a, we say that b is a __________ of a.

For given integers a and b, the extended __________ algorithm not only calculates

the greatest common divisor d but also two additional integers x and y.

AES uses a Feistel structure.

At each horizontal point, State is the same for both encryption and

decryption.

DES is a block cipher intended to replace AES for commercial

applications.

The nonlinearity of the S-box is due to the use of the multiplicative

inverse.

Virtually all encryption algorithms, both conventional and publickey,

involve arithmetic operations on integers.

The Advanced Encryption Standard was published by the __________ in 2001.

In Advanced Encryption Standard all operations are performed on __________

bytes.

The AES cipher begins and ends with a(n) _________ stage because any other stage,

applied at the beginning or end, is reversible without knowledge of the key and

would add no security.

A. B.

C. D.

A __________ is a set in which you can do addition, subtraction, multiplication and

division without leaving the set.

Division requires that each nonzero element have a(n) __________ inverse.

In the AES structure both encryption and decryption ciphers begin with a(n)

__________ stage, followed by nine rounds that each include all four stages,

followed by a tenth round of three stages.

The final round of both encryption and decryption of the AES structure consists

of __________ stages.

AES can be implemented very efficiently on an 8-bit processor.

The first row of State is not altered; for the second row a 1-byte circular left

shift is performed; for the third row a 2-byte circular left shift is performed; and

for the fourth row a 3-byte circular left shift is performed. This transformation

is called __________ .

In the AddRoundKey transformation the 128 bits of State are bitwise XORed

with the _________ of the round key.

The vast majority of network based symmetric cryptographic applications make use of stream ciphers.

DES uses a 56-bit block and a 64-bit key.

If the bit-stream generator is a key-controlled algorithm the two

users only need to share the generating key and then each can

produce the keystream.

A problem with the ideal block cipher using a small block size is

that it is vulnerable to a statistical analysis of the plaintext.

All other things being equal, smaller block sizes mean greater

security.

A sequence of plaintext elements is replaced by a __________ of that sequence

which means that no elements are added, deleted or replaced in the

sequence, but rather the order in which the elements appear in the sequence

is changed.

A __________ cipher is one that encrypts a digital data stream one bit or one

byte at a time.

The vast majority of network-based symmetric cryptographic applications

make use of ________ ciphers.

A __________ cipher is one in which a block of plaintext is treated as a whole

and used to produce a ciphertext block of equal length.

__________ is when each plaintext element or group of elements is uniquely

replaced by a corresponding ciphertext element or group of elements.

Key sizes of __________ or less are now considered to be inadequate.

Feistel proposed that we can approximate the ideal block cipher by utilizing

the concept of a __________ cipher, which is the execution of two or more

simple ciphers in sequence in such a way that the final result or product is

cryptographically stronger than any of the component ciphers.

The criteria used in the design of the __________ focused on the design of the

S-boxes and on the P function that takes the output of the S-boxes.

The greater the number of rounds, the __________ it is to perform cryptanalysis.

A prime concern with DES has been its vulnerability to brute-force

attack because of its relatively short key length.

Once the plaintext is converted to ciphertext using the encryption algorithm the plaintext is then used as input and the algorithm is applied again

A mode of operation is a technique for enhancing the effect of a  cryptographic algorithm or adapting the algorithm for an     application. 

The XTS-AES standard describes a method of decryption for data         stored in sector-based devices where the threat model includes         possible access to stored data by the adversary. 

S-AES is the most widely used multiple encryption scheme. 

Given the potential vulnerability of DES to a brute-force attack, an         alternative has been found. 

There are no practical cryptanalytic attacks on 3DES.

A number of Internet based applications have adopted two-key

3DES, including PGP and S/MIME.

The sender is the only one who needs to know an initialization

vector.

A typical application of Output Feedback mode is stream oriented

transmission over noisy channel, such as satellite communication.

Cipher Feedback (CFB) is used for the secure transmission of

single values.

In the first instance of multiple encryption plaintext is converted to __________

using the encryption algorithm.

Triple DES makes use of __________ stages of the DES algorithm, using a total of

two or three distinct keys.

Another important mode, XTS-AES, has been standardized by the __________

Security in Storage Working Group.

A. B.

C. D.

The _________ and _________ block cipher modes of operation are used for

authentication.

__________ modes of operation have been standardized by NIST for use with

symmetric block ciphers such as DES and AES.

The output of the encryption function is fed back to the shift register in

Output Feedback mode, whereas in ___________ the ciphertext unit is fed back

to the shift register.

A. B.

C. D.

The simplest form of multiple encryption has __________ encryption stages and

__________ keys.

The __________ algorithm will work against any block encryption cipher and

does not depend on any particular property of DES.

_________ mode is similar to Cipher Feedback, except that the input to the encryption algorithm is the preceding DES output.

Symmetric encryption remains by far the most widely used of the two types of encryption.

Rotor machines are sophisticated precomputer hardware devices that use substitution techniques.

Symmetric encryption is a form of cryptosystem in which encryption and decryption are performed using different keys. It is also known as non- conventional encryption.

With the use of symmetric encryption, the principal security problem is maintaining the secrecy of the key.

The process of converting from plaintext to ciphertext is known as deciphering or decryption.

The algorithm will produce a different output depending on the specific secret key being used at the time. The exact substitutions and transformations performed by the algorithm depend on the key.

When using symmetric encryption it is very important to keep the algorithm secret.

On average, half of all possible keys must be tried to achieve success with a brute-force attack.

Ciphertext generated using a computationally secure encryption scheme is impossible for an opponent to decrypt simply because the required information is not there.

Monoalphabetic ciphers are easy to break because they reflect the frequency data of the original alphabet.

               techniques map plaintext elements (characters, bits) into ciphertext elements.

Joseph Mauborgne proposed an improvement to the Vernam cipher that uses a random key that is as long as the message so that the key does not need to be repeated. The key is used to encrypt and decrypt a single message and then is discarded. Each new message requires a new key of the same

length as the new message. This scheme is known as a(n)                     .

An original intelligible message fed into the algorithm as input is known as

                  , while the coded message produced as output is called the                  .

Restoring the plaintext from the ciphertext is                     .

A                     attack involves trying every possible key until an intelligible translation of the ciphertext is obtained.

Techniques used for deciphering a message without any knowledge of the enciphering details is            .

The       takes the ciphertext and the secret key and produces the original plaintext. It is essentially the encryption algorithm run in reverse

If both sender and receiver use the same key, the system is referred to as:

               attacks exploit the characteristics of the algorithm to attempt to deduce a specific plaintext or to deduce the key being used.

The                     was used as the standard field system by the British Army in World War I and was used by the U.S. Army and other Allied forces during World War II.