# Cryptography and Digital Signatures

Topics: Cryptography, Cryptographic hash function, Digital signature Pages: 2 (426 words) Published: August 27, 2013
Cryptool
CrypTool is an open source tool that illustrates cryptographic and cryptanalytic concepts. CrypTool implements more than 200 algorithms. In CrypTool, users are able to adjust the parameters to their own specific needs. Cryptool introduces the user to the field of cryptography. Classical ciphers alongside with asymmetric cryptography, to include RSA, elliptic curve cryptography, digital signatures, homomorphic encryption, and Diffie-Hellman key exchange. CrypTool also contains some didactical games, and an animated tutorial about primes and elementary number theory (Cryptool, 2013).

The development of CrypTool was started back in 1998, by a group of German companies and universities, but now is an open source project. More than sixty people worldwide contribute regularly to the project. The goal of the CrypTool is to help ensure users are aware of how cryptography can help against network security threats and also explains the underlying concepts of cryptology. The software is available in English, German, Polish, Spanish, and Serbian (Wikia.com, 2013).

Currently under NIST there are three approved algorithms that can be used when generating and verifying digital signatures. These three algorithms are DSA, RSA, and ECDSA, which are used in conjunction with an approved Hash Function. The hash functions in Cryptool that are approved for use by NIST for digital signatures are MD5, SHA-1, and SHA-256. And the digital signature found in Cryptool 2.0 is RSA (NIST, 2013).

NIST standards for RSA digital signature key sizes are 1024, 2048, and 3072 bits. Government agencies must generate digital signatures using at least one of these three choices. The security strength associated with the RSA digital signature process is no greater than the minimum of the security strength associated with the bit length of the modulus and the security strength of the hash function that is employed (NIST, 2009 p. 22).

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References: CrypTool, (2013). CrypTool Portal. Retrieved August 22, 2013 from
http://www.cryptool.org/en/
NIST, (2013). Secure Hashing. Retrieved August 22, 2013 from
http://csrc.nist.gov/groups/ST/toolkit/secure_hashing.html
NIST, (2009). Federal Information Processing Standards Publication 186-3. Retrieved August
22, 2013 from http://csrc.nist.gov/publications/fips/fips186-3/fips_186-3.pdf
Wikia.com, (2013). CrypTool. Retrieved August 22, 2013 from
http://cryptography.wikia.com/wiki/CrypTool