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WGU C839 Exam: Questions With Correct Solutions
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WGU C839 Exam: Questions With Correct Solutions
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WGU C839 Exam: Questions With Correct Solutions________ is an alternative to PKI (Public Key Infrastructure), and involves
generating the encryption key from a piece of the identity of the recipient.
Right Ans - Identity-based Encryption (IBE) is an alternative to PKI (Public
Key Infrastructure), and involves generating the encryption key from a piece
of the identity of the recipient such an email address or similar
____ calculations can be used to justify that RSA works correctly and
accurately, i.e. prove that the decrypted message is indeed the original
message from the sender. Right Ans - Fermat's little theorem is used to
justify RSA. We use the Fermat's Little Theorem to prove that RSA works
correctly and accurately. In other words, the decrypted message is indeed the
original message from the sender.
Steve is looking for a mechanism to use to for generating RSA private keys and
does not have budget to leverage any pricey solution. What would you
recommend Steve look into as a potential solution? Right Ans - OpenSSL is
an open-source command line tool that is commonly used to generate private
keys, create CSRs, install your SSL/TLS certificate, and identify certificate
information
With Bitcoins, the _____ key defines our identity and we use it to sign for
transactions, and prove our identity to others with the ______ key when making
use of ECC. Right Ans - With Bitcoins, the private key defines our identity
and we use it to sign for transactions, and prove our identity to others with
the public key.
Select the options from the list below that support some form of
homomorphic encryption. Select all that apply. Right Ans - With
homomorphic encryption, we can perform mathematical operations with
ciphered values. For RSA, we have a partially homomorphic cryptosystem,
where we can take two values and the cipher them. Next we multiply the
results together, and the deciphered result will be the multiplication of the
two values. RSA is a partially homomorphic crypto system.
The Paillier cryptosystem supports homomorphic encryption, where two
encrypted values can be added together, and the decryption of the result gives
the addition
, What methods can be use to overcome the weakness in Diffie Hellman
involving the ease at which values of Diffie Hellman parameters that use the
DHE_EXPORT cipher set are precomputed? Select all that apply. Right Ans -
The ways to overcome the problems are to:
• Disable Export Cipher Suites. With this we disable any negotiation of the key
using export grade ciphers. This will have no effect on connections, as no
existing version of Web browsers actually depend on export level ciphers.
• Use (Ephemeral) Elliptic-Curve Diffie-Hellman (ECDHE). This method uses a
key exchange method based on an Elliptic-Curve DiffieHellman (ECDH) key
exchange.
• Uses a strong group. With this we make sure that we are using the strong
generation of a prime number which cannot be precomputing. Currently
2,048-bit prime numbers are recommended. A strong prime number is
generated with "openssl dhparam -out dhparams.pem 2048". Normally this
will take a few minutes to compute, as it involves a random process, so can
only be used to statically assign the parameters.
Diffie Hellman group 1 uses a _____-bit prime number. Right Ans - The
strength of the Diffie-Hellman method normally relates to the size of the
prime number bases which are used in the key exchange, where Group 5 uses
a 1,536-bit prime number, Group 2 uses a 1,024-bit prime, and Group 1 uses a
768-bit prime number.
With key exchange we typically have a time-out for the key to be used. At the
end of this period what happens to the key? Right Ans - With key exchange
we typically have a time-out for the key to be used, after which time the key is
renegotiated.
_____-bit prime numbers is the minimum recommended for use with Diffie
Hellman to counter attacks involving key precomputation. Right Ans - Uses
a strong group. With this we make sure that we are using the strong
generation of a prime number which cannot be precomputing. Currently
2,048-bit prime numbers are recommended. A strong prime number is
generated with "openssl dhparam -out dhparams.pem 2048". Normally this
will take a few minutes to compute, as it involves a random process, so can
only be used to statically assign the parameters.
Regarding keys generated for Diffie Hellman operations, what is the difference
between a static key and a ephemeral key? Right Ans - The keys can either
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