WGU C839 INTRO TO CRYPTOGRAPHY MASTER SET
QUESTIONS AND CORRECT DETAILED ANSWERS
(VERIFIED ANSWERS) |ALREADY GRADED A+||BRAND NEW
A technique that is based on how frequently certain letters appear in
English versus others. Ans✓✓✓ Frequency Analysis
8-bit values, up to 256 characters Ans✓✓✓ ASCII
16-bit values, up to 65,536 Ans✓✓✓ UTF-16
ECB, CBC, CFB, OFB, and CTR. Ans✓✓✓ Common block cipher
modes include:
-Most basic, weak , and unsecure
-Each block is processed separately
-No Salt or IV is used and the same key will be used to encrypt
each block. This means if a given plaintext is encrypted in ECB
and results in a given ciphertext, that same ciphertext will be
output EVERY TIME the same plaintext is encrypted . Ans✓✓✓ ECB
(Electronic Code Book)
- Minor step up from ECB with the incorporation of an
initialization vector for the first block.
- Results of encryption from previous block is input into to
,encryption process of the current block. Ans✓✓✓ CBC (Cipher Block
Chaining)
-Converts the block cipher into a self synchronizing stream cipher.
-Current block takes output of the XOR process Ans✓✓✓ CFB (Cipher
Feedback)
- Converts the block cipher to a synchronous stream output
- Current block takes output from the cipher stage
- The first stage takes the data blocks and X ORs it with the
encrypted version of the IV value. The output of the first stage
encryption is then feed into the next stage, and encrypted, with
the output being XOR'ed with the second block. Ans✓✓✓ OFB (Output
Feedback)
- Converts the block cipher into a stream cipher
- Generates a counter value and a nonce , and encrypts this, in
order to XOR with the plain text block.
- The advantage of CTR is that each block is processed
independent of the others, facilitating ability to conduct
parallel processing of blocks . i.e., feedback from other stages
to feed into the current one is not required. Ans✓✓✓ Counter Mode
(CTR)
,identity checking and key protection Ans✓✓✓ The main applications
of public key encryption
Mathematical operations performed on ciphered values i.e., before
decryption. Ans✓✓✓ Homomorphic encryption
____is a public key method that is used in both encryption and digital
signing. It is used in many applications and uses discrete logarithms.
Ans✓✓✓ El Gamal
____ is a public key encryption method that is an extension of El Gamal
but adds a one way hashing method which protects against an adaptive
chosen ciphertext attack. Ans✓✓✓ Cramer-Shoup
Step 1: [Sender signs] Sender signs message with sender's own private
key
Step 2: Sender Encrypts ] Sender encrypts message with receiver's
public key
Step 3: [Receiver Decrypts] Receiver decrypts message with receiver's
own private key
Step 4: [Receiver verifies] Receiver verifies message with sender's
public key Ans✓✓✓ 4 steps to send a digitally signed message using
public key cryptography...
What cryptosystem supports homomorphic encryption? Ans✓✓✓ What
cryptosystem supports homomorphic encryption? Paillier
, Step 1: [Sender signs] Sender produces a hash of the message and
encrypts it using sender's private key
Step 2: [Sender Encrypts] Sender packages up [original message +
encrypted hash] and encrypts both with the receiver's public key
Step 3: [Receiver Decrypts] Receiver decrypts packaged up [original
message + encrypted hash] with receiver's private key
Step 4: [Receiver verifies] Receiver decrypts the encrypted hash with
sender's public key
Step 5: [Receiver verifies] Receiver computes hash of the original
message and compares to the now decrypted original hash to ensure they
match. Ans✓✓✓ The 5 basic steps to send a confidential, authenticated
message that incorporates hashing
ensure integrity are as follows:
-IKE
-PKCS #7
-PKCS #10
-RSA signatures
-X.509v3 Ans✓✓✓ Common certificate types
When a digital signature is created, whether self generated/signed or by
a trusted well known Certificate Authority (CA) such as Verisign or
Entrust, the certificate will contain the public key of the certificate
owner. Ans✓✓✓ Passing PKI public keys in a verifiable way.
QUESTIONS AND CORRECT DETAILED ANSWERS
(VERIFIED ANSWERS) |ALREADY GRADED A+||BRAND NEW
A technique that is based on how frequently certain letters appear in
English versus others. Ans✓✓✓ Frequency Analysis
8-bit values, up to 256 characters Ans✓✓✓ ASCII
16-bit values, up to 65,536 Ans✓✓✓ UTF-16
ECB, CBC, CFB, OFB, and CTR. Ans✓✓✓ Common block cipher
modes include:
-Most basic, weak , and unsecure
-Each block is processed separately
-No Salt or IV is used and the same key will be used to encrypt
each block. This means if a given plaintext is encrypted in ECB
and results in a given ciphertext, that same ciphertext will be
output EVERY TIME the same plaintext is encrypted . Ans✓✓✓ ECB
(Electronic Code Book)
- Minor step up from ECB with the incorporation of an
initialization vector for the first block.
- Results of encryption from previous block is input into to
,encryption process of the current block. Ans✓✓✓ CBC (Cipher Block
Chaining)
-Converts the block cipher into a self synchronizing stream cipher.
-Current block takes output of the XOR process Ans✓✓✓ CFB (Cipher
Feedback)
- Converts the block cipher to a synchronous stream output
- Current block takes output from the cipher stage
- The first stage takes the data blocks and X ORs it with the
encrypted version of the IV value. The output of the first stage
encryption is then feed into the next stage, and encrypted, with
the output being XOR'ed with the second block. Ans✓✓✓ OFB (Output
Feedback)
- Converts the block cipher into a stream cipher
- Generates a counter value and a nonce , and encrypts this, in
order to XOR with the plain text block.
- The advantage of CTR is that each block is processed
independent of the others, facilitating ability to conduct
parallel processing of blocks . i.e., feedback from other stages
to feed into the current one is not required. Ans✓✓✓ Counter Mode
(CTR)
,identity checking and key protection Ans✓✓✓ The main applications
of public key encryption
Mathematical operations performed on ciphered values i.e., before
decryption. Ans✓✓✓ Homomorphic encryption
____is a public key method that is used in both encryption and digital
signing. It is used in many applications and uses discrete logarithms.
Ans✓✓✓ El Gamal
____ is a public key encryption method that is an extension of El Gamal
but adds a one way hashing method which protects against an adaptive
chosen ciphertext attack. Ans✓✓✓ Cramer-Shoup
Step 1: [Sender signs] Sender signs message with sender's own private
key
Step 2: Sender Encrypts ] Sender encrypts message with receiver's
public key
Step 3: [Receiver Decrypts] Receiver decrypts message with receiver's
own private key
Step 4: [Receiver verifies] Receiver verifies message with sender's
public key Ans✓✓✓ 4 steps to send a digitally signed message using
public key cryptography...
What cryptosystem supports homomorphic encryption? Ans✓✓✓ What
cryptosystem supports homomorphic encryption? Paillier
, Step 1: [Sender signs] Sender produces a hash of the message and
encrypts it using sender's private key
Step 2: [Sender Encrypts] Sender packages up [original message +
encrypted hash] and encrypts both with the receiver's public key
Step 3: [Receiver Decrypts] Receiver decrypts packaged up [original
message + encrypted hash] with receiver's private key
Step 4: [Receiver verifies] Receiver decrypts the encrypted hash with
sender's public key
Step 5: [Receiver verifies] Receiver computes hash of the original
message and compares to the now decrypted original hash to ensure they
match. Ans✓✓✓ The 5 basic steps to send a confidential, authenticated
message that incorporates hashing
ensure integrity are as follows:
-IKE
-PKCS #7
-PKCS #10
-RSA signatures
-X.509v3 Ans✓✓✓ Common certificate types
When a digital signature is created, whether self generated/signed or by
a trusted well known Certificate Authority (CA) such as Verisign or
Entrust, the certificate will contain the public key of the certificate
owner. Ans✓✓✓ Passing PKI public keys in a verifiable way.
