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SOLUTION

DSA/DSS

The Digital Signature Standard (DSS) was developed by the U.S. National Security Agency and adopted as a Federal Information Processing Standard (FIPS) by the National Institute for Standards and Technology. DSS is based on the Digital Signature Algorithm (DSA). Although DSA allows keys of any length, only keys between 512 and 1,024 bits are permitted under the DSS FIPS. As specified, DSS can be used only for digital signatures, although it is possible to use some DSA implementations for encryption as well.

RSA

RSA is a well-known public key cryptography system developed in 1977 by three professors at MIT: Ronald Rivest, Adi Shamir, and Leonard Adleman. RSA can be used both for encrypting information and as the basis of a digital signature system. Digital signatures can be used to prove the authorship and authenticity of digital information. The key can be any length, depending on the particular implementation used.

Elliptic curves

Public key systems have traditionally been based on factoring (RSA), discrete logarithms (Diffie-Helman), and the knapsack problem. Elliptic curve cryptosystems are public key encryption systems that are based on an elliptic curve rather than on a traditional logarithmic function; that is, they are based on solutions to the equation y2 = x3 + ax + b. The advantage to using elliptic curve systems stems from the fact that there are no known subexponential algorithms for computing discrete logarithms of elliptic curves. Thus, short keys in elliptic curve cryptosystems can offer a high degree of privacy and security, while remaining easily calculatable. Elliptic curves can be computed very efficiently in hardware. Certicom (http://www.certicom.com) has attempted to commercialize implementations of elliptic curve cryptosystems for use in mobile computing.

Advantages for Public Key Encryption


Two of the most common uses for public key cryptography are encrypted messaging and digital signatures:

With encrypted messaging, a person who wishes to send an encrypted message to a particular recipient encrypts that message with the individual's public key. The message can then be decrypted only by the authorized recipient.

With digital signatures, the sender of the message uses the public key algorithm and a private key to digitally sign a message. Anyone who receives the message can then validate the authenticity of the message by verifying the signature with the sender's public key.
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As you have studied some popular public key algorithms:

1) DSS – Digital Signature Standard based on DSA (Digital Standard Algorithm) –
2) RSA
3) Elliptic Curves

Question: [10 Marks]

You are required to provide answers for the given below questions:

1) Differences among the above listed Public Key Algorithms.
Note: One of the differences must contain information that describes the “practical usage” of the particular Algorithm currently.
2) Advantages and disadvantages for the most common and efficient public key
Algorithm applied now a days.

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