C storing the public keys takes more space than

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C. Storing the public keys takes more space than previously believed. D. Not enough computing power exists to encrypt and decrypt all the e-mail traffic. Answer: A See Chapter 7. The web of trust can become very large and potentially weak in places. 110 What party in an organization signs a subscriber’s digital certificate? A. Repository B. Subscriber’s supervisor C. Subscriber D. Certificate Authority Answer: D See Chapter 7. The Certificate Authority (CA), after receiving satisfactory proof of the identity of the individual, signs that individual’s certificate. 111 The science of hiding the true meaning of messages from unintended recipients is known as A. Cryptosystem B. Cryptology C. Cryptography D. Enciphering Answer: C See Chapter 7. Cryptography is the art of hiding the meaning of messages so that unintended recipients can’t read those messages. 112 Which protocol is most often used to access certificates in a PKI? A. SSL B. LDAP C. CA D. SSH Answer: B See Chapter 7. Lightweight Directory Access Protocol (LDAP) is the directory agent of choice for Public Key Infrastructures (PKIs). 113 One of the challenges facing participants in a symmetric key cryptosystem is A. How to tell each user which algorithm to use B. How to safely transmit the secret key to each user C. How to transmit enciphered messages
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D. How to store deciphered messages Answer: B See Chapter 7. Getting the secret key to each user can be difficult because it must not be made available to any unauthorized party. 114 The type of encryption used by Caesar was A. One-time pad B. Transposition C. Transformation D. Substitution Answer: D See Chapter 7. Caesar used substitution; specifically, by shifting the alphabet by three letters. 115 Which of the following is NOT a purpose of a digital signature? A. Authentication to a key server B. Detecting unauthorized changes of data C. Non-repudiation D. Identifying the person who signed the data Answer: A See Chapter 7. Digital signatures aren't used for authentication to a key server, but the other three are stated uses of digital signatures. 116 A given symmetric cryptosystem uses a 64-bit key size. If an asymmetric cryptosystem is used instead, what key size is required to give the equivalent strength of the symmetric cryptosystem? A. 2048 bits B. 512 bits C. 64 bits D. 24 bits Answer: B See Chapter 7. An asymmetric cryptosystem must use a 512-bit key size to match the strength of a symmetric cryptosystem using a 64- bit key. 117 How can symmetric key cryptosystems be made more secure? A. By periodically changing the secret key B. By periodically changing the length of the secret key C. By canceling and reissuing secret keys D. By periodically changing the encryption algorithm Answer: A See Chapter 7. By changing the secret key periodically, only a finite portion of the ciphertext can be broken by someone who has discovered the secret key.
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118 A cipher that rearranges the order of characters from the original message is a A. Substitution cipher B. Transfiguration cipher C. Transubstantiation cipher D. Transposition cipher Answer: D See Chapter 7. Transposition is the process of changing the order of characters in a message.
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