WGU C836: Questions With Objective Solutions
Cryptology Correct Answer - is the study of cryptographic algorithms. •
These algorithms convert plaintext (original message) into ciphertext
(encrypted/new message).
Cryptanalysis Correct Answer - is the breaking and finding a weakness
in the given algorithm
. Correct Answer - Some algorithms work in both directions allowing for
the ciphertext to return to the original plaintext form. Other algorithms act as
an integrity check only allowing a one-way function.
. Correct Answer - History is rich with the use of cryptography, with
some of the oldest examples being used by the ancient Greeks and Romans.
Information was hidden by a wide variety of codes, one extreme example was
by tattooing them on the shaved heads of messengers and then allowing the
hair to grow, and by a multitude of other methods generally focused on
mathematical algorithms.
Caesar cipher Correct Answer - The Caesar cipher is based on
transposition and involves shifting each letter of the plaintext message by a
certain number of letters, historically three. The ciphertext can be decrypted
by applying the same number of shifts in the opposite direction. This type of
encryption is known as a substitution cipher, due to the substitution of one
letter for another in a consistent fashion.
ROT13 Correct Answer - ROT13 uses the same mechanism as the Caesar
cipher but moves each letter 13 places forward. The convenience of moving
13 places lies in the fact that applying another round of encryption with
ROT13 also functions as decryption, as two rotations will return us to the
original starting place in the alphabet.
Cryptographic Machines Correct Answer - Before the advent of the
modern computer, machines existed that simplified the use of encryption and
made more complex encryption schemes feasible. Initially, such devices were
simple mechanical machines, but as technology progressed, we began to see
the inclusion of electronics and considerably more complex systems
,The Jefferson Disk Correct Answer - invented by Thomas Jefferson in
1795, is a purely mechanical cryptographic machine. It is composed of a series
of disks, each marked with the letters a to z around its edge. On each disk, the
letters are arranged in a different order; each disk is also marked with a
unique designator to facilitate arranging them in a particular order. The
device built by Jefferson contained 36 disks, with each disk representing one
character in the message.
German Enigma Correct Answer - The Enigma was created by Arthur
Scherbius in 1923 and was used to secure German communications during
World War II. In fact, there were several models of Enigma machine, and a
variety of accessories and add-ons that could be attached to them. The Enigma
I, was developed in 1932.
Enigma Correct Answer - The ___________ was based on a series of wheels,
referred to as rotors, each with 26 letters and 26 electrical contacts on them,
similar in general concept to the Jefferson Disk.
. Correct Answer - In order for two Enigma machines to communicate,
they needed to be configured identically. The rotors needed to be the same
and in the same position, the rings marked with the alphabet on each rotor
needed to be in the same position, the rotors needed to be set to the same
starting position, and any plugs in the plugboard needed to be configured in
the same fashion
Kerckhoffs' Principle Correct Answer - the second principle has become
a tenet of cryptographic algorithms. This idea was later restated by Claude
Shannon as "the enemy knows the system"Both versions of this concept mean
that cryptographic algorithms should be robust enough that, even though
someone may know every bit of the system with the exception of the key
itself, he or she should still not be able to break the encryption
. Correct Answer - This idea represents the opposite approach to
"security through obscurity" and is one of the underlying principles for many
modern cryptographic systems.
protecting data at rest and protecting data in motion. Correct Answer -
We can divide practical uses of cryptography into two major categories
,Protecting data at rest Correct Answer - is important because of the
large amount of stored data that can be found on devices such as backup
tapes, flash drives, and hard drives in portable devices such as laptops
Protecting data in motion Correct Answer - is vital as well because of the
enormous amount of business that is conducted over the Internet, including
financial transactions, medical information, tax filings, and other similarly
sensitive exchanges
Symmetric cryptography Correct Answer - ________________ ______, also
known as private key cryptography, utilizes a single key for both encryption of
the plaintext and decryption of the ciphertext.
Asymmetric cryptography Correct Answer - ______________ , also known as
public key cryptography, utilizes two keys: a public key and a private key. The
public key is used to encrypt data sent from the sender to the receiver and is
shared with everyone.
Hash functions: Correct Answer - represent a third cryptography type
alongside symmetric and asymmetric cryptography, what we might call
keyless cryptography. _____________ also referred to as message digests, do not
use a key, but instead create a largely unique and fixed-length hash value,
commonly referred to as a hash, based on the original message, something
along the same lines as a fingerprint. Any slight change to the message will
change the hash
Digital signatures: Correct Answer - _____________ allow us to sign a
message in order to enable detection of changes to the message contents, to
ensure that the message was legitimately sent by the expected party, and to
prevent the sender from denying that he or she sent the message, known as
nonrepudiation.
Certificates: Correct Answer - ___________ are created to link a public key
to a particular individual and are often used as a form of electronic
identification for that particular person. A certificate is typically formed by
taking the public key and identifying information, such as a name and address,
and having them signed by a certificate authority (CA).
, block ciphers and stream ciphers Correct Answer - Symmetric key
cryptography makes use of two types of ciphers
Block cipher Correct Answer - takes a predetermined number of bits,
known as a block, in the plaintext message and encrypts that block. Blocks are
commonly composed of 64 bits but can be larger or smaller depending on the
particular algorithm being used and the various modes in which the algorithm
might be capable of operating.
Stream cipher Correct Answer - encrypts each bit in the plaintext
message, 1 bit at a time.
. Correct Answer - A large majority of the encryption algorithms in use at
present are block ciphers. Although block ciphers are often slower than
stream ciphers, they tend to be more efficient. Since block ciphers operate on
larger blocks of the message at a time, they do tend to be more resource
intensive and are more complex to implement in hardware or software
Block ciphers Correct Answer - ____________ are also more sensitive to
errors in the encryption process as they are working with more data. An error
in the encryption process of a block cipher may render unusable a larger
segment of data than what we would find in a stream cipher, as the stream
cipher would only be working with 1 particular bit
DES Correct Answer - is a block cipher based on symmetric key
cryptography and uses a 56-bit key. Although DES was considered to be very
secure for some period of time, it is no longer considered to be so.
3DES Correct Answer - which is simply DES used to encrypt each block
three times, each time with a different key. DES can operate in several
different block modes, including Cipher Block Chaining (CBC), Electronic
CodeBook (ECB), Cipher Feedback (CFB), Output Feedback (OFB), and
Counter Mode (CTR). Each mode changes the way encryption functions and
the way errors are handled.
AES Correct Answer - is a set of symmetric block ciphers endorsed by
the US government through NIST, and now used by a variety of other
organizations, and is the replacement for DES as the standard encryption
algorithm for the US federal government. AES uses three different ciphers: one
Cryptology Correct Answer - is the study of cryptographic algorithms. •
These algorithms convert plaintext (original message) into ciphertext
(encrypted/new message).
Cryptanalysis Correct Answer - is the breaking and finding a weakness
in the given algorithm
. Correct Answer - Some algorithms work in both directions allowing for
the ciphertext to return to the original plaintext form. Other algorithms act as
an integrity check only allowing a one-way function.
. Correct Answer - History is rich with the use of cryptography, with
some of the oldest examples being used by the ancient Greeks and Romans.
Information was hidden by a wide variety of codes, one extreme example was
by tattooing them on the shaved heads of messengers and then allowing the
hair to grow, and by a multitude of other methods generally focused on
mathematical algorithms.
Caesar cipher Correct Answer - The Caesar cipher is based on
transposition and involves shifting each letter of the plaintext message by a
certain number of letters, historically three. The ciphertext can be decrypted
by applying the same number of shifts in the opposite direction. This type of
encryption is known as a substitution cipher, due to the substitution of one
letter for another in a consistent fashion.
ROT13 Correct Answer - ROT13 uses the same mechanism as the Caesar
cipher but moves each letter 13 places forward. The convenience of moving
13 places lies in the fact that applying another round of encryption with
ROT13 also functions as decryption, as two rotations will return us to the
original starting place in the alphabet.
Cryptographic Machines Correct Answer - Before the advent of the
modern computer, machines existed that simplified the use of encryption and
made more complex encryption schemes feasible. Initially, such devices were
simple mechanical machines, but as technology progressed, we began to see
the inclusion of electronics and considerably more complex systems
,The Jefferson Disk Correct Answer - invented by Thomas Jefferson in
1795, is a purely mechanical cryptographic machine. It is composed of a series
of disks, each marked with the letters a to z around its edge. On each disk, the
letters are arranged in a different order; each disk is also marked with a
unique designator to facilitate arranging them in a particular order. The
device built by Jefferson contained 36 disks, with each disk representing one
character in the message.
German Enigma Correct Answer - The Enigma was created by Arthur
Scherbius in 1923 and was used to secure German communications during
World War II. In fact, there were several models of Enigma machine, and a
variety of accessories and add-ons that could be attached to them. The Enigma
I, was developed in 1932.
Enigma Correct Answer - The ___________ was based on a series of wheels,
referred to as rotors, each with 26 letters and 26 electrical contacts on them,
similar in general concept to the Jefferson Disk.
. Correct Answer - In order for two Enigma machines to communicate,
they needed to be configured identically. The rotors needed to be the same
and in the same position, the rings marked with the alphabet on each rotor
needed to be in the same position, the rotors needed to be set to the same
starting position, and any plugs in the plugboard needed to be configured in
the same fashion
Kerckhoffs' Principle Correct Answer - the second principle has become
a tenet of cryptographic algorithms. This idea was later restated by Claude
Shannon as "the enemy knows the system"Both versions of this concept mean
that cryptographic algorithms should be robust enough that, even though
someone may know every bit of the system with the exception of the key
itself, he or she should still not be able to break the encryption
. Correct Answer - This idea represents the opposite approach to
"security through obscurity" and is one of the underlying principles for many
modern cryptographic systems.
protecting data at rest and protecting data in motion. Correct Answer -
We can divide practical uses of cryptography into two major categories
,Protecting data at rest Correct Answer - is important because of the
large amount of stored data that can be found on devices such as backup
tapes, flash drives, and hard drives in portable devices such as laptops
Protecting data in motion Correct Answer - is vital as well because of the
enormous amount of business that is conducted over the Internet, including
financial transactions, medical information, tax filings, and other similarly
sensitive exchanges
Symmetric cryptography Correct Answer - ________________ ______, also
known as private key cryptography, utilizes a single key for both encryption of
the plaintext and decryption of the ciphertext.
Asymmetric cryptography Correct Answer - ______________ , also known as
public key cryptography, utilizes two keys: a public key and a private key. The
public key is used to encrypt data sent from the sender to the receiver and is
shared with everyone.
Hash functions: Correct Answer - represent a third cryptography type
alongside symmetric and asymmetric cryptography, what we might call
keyless cryptography. _____________ also referred to as message digests, do not
use a key, but instead create a largely unique and fixed-length hash value,
commonly referred to as a hash, based on the original message, something
along the same lines as a fingerprint. Any slight change to the message will
change the hash
Digital signatures: Correct Answer - _____________ allow us to sign a
message in order to enable detection of changes to the message contents, to
ensure that the message was legitimately sent by the expected party, and to
prevent the sender from denying that he or she sent the message, known as
nonrepudiation.
Certificates: Correct Answer - ___________ are created to link a public key
to a particular individual and are often used as a form of electronic
identification for that particular person. A certificate is typically formed by
taking the public key and identifying information, such as a name and address,
and having them signed by a certificate authority (CA).
, block ciphers and stream ciphers Correct Answer - Symmetric key
cryptography makes use of two types of ciphers
Block cipher Correct Answer - takes a predetermined number of bits,
known as a block, in the plaintext message and encrypts that block. Blocks are
commonly composed of 64 bits but can be larger or smaller depending on the
particular algorithm being used and the various modes in which the algorithm
might be capable of operating.
Stream cipher Correct Answer - encrypts each bit in the plaintext
message, 1 bit at a time.
. Correct Answer - A large majority of the encryption algorithms in use at
present are block ciphers. Although block ciphers are often slower than
stream ciphers, they tend to be more efficient. Since block ciphers operate on
larger blocks of the message at a time, they do tend to be more resource
intensive and are more complex to implement in hardware or software
Block ciphers Correct Answer - ____________ are also more sensitive to
errors in the encryption process as they are working with more data. An error
in the encryption process of a block cipher may render unusable a larger
segment of data than what we would find in a stream cipher, as the stream
cipher would only be working with 1 particular bit
DES Correct Answer - is a block cipher based on symmetric key
cryptography and uses a 56-bit key. Although DES was considered to be very
secure for some period of time, it is no longer considered to be so.
3DES Correct Answer - which is simply DES used to encrypt each block
three times, each time with a different key. DES can operate in several
different block modes, including Cipher Block Chaining (CBC), Electronic
CodeBook (ECB), Cipher Feedback (CFB), Output Feedback (OFB), and
Counter Mode (CTR). Each mode changes the way encryption functions and
the way errors are handled.
AES Correct Answer - is a set of symmetric block ciphers endorsed by
the US government through NIST, and now used by a variety of other
organizations, and is the replacement for DES as the standard encryption
algorithm for the US federal government. AES uses three different ciphers: one
