ccna basic knowledge pdf

ccna basic knowledge pdf. RSA encryption algorithm.7.4 Public Key Cryptography 207 EIGamal.Elliptic curve secrecy algorithms.Although each algorithm has a different mathematical basis, they all share the common feature that the computations required are complex. Their design is based on computational problems, such as decomposing the very large numbers or computing the discrete logarithms of the very large numbers. The result is that computation takes up most of the time of asymmetric algorithms. In fact, asymmetric algorithms may be at most 1,000 times slower than symmetric algorithms. Due to the lack of speed, asymmetric algorithms are often used in cryptographic mechanisms where the total amount is not large, such as key exchange and digital signatures where there is no internal key exchange technology.Key management for asymmetric algorithms will generally be simpler than for symmetric algorithms because usually one of the two keys used for encryption or decryption will be made public. Typical key lengths for asymmetric algorithms range from 512.4096 bits. For most algorithms, a key length greater than or equal to 1024 is considered trustworthy, while a key length shorter than 1024 bits is considered unreliable. It is not meaningful to compare the key lengths of asymmetric and symmetric algorithms because the underlying designs of the two algorithms differ significantly. To illustrate this point, it is generally accepted that a 2 048-bit encryption key for RSA is roughly equivalent to a 128-bit key for RC4 in terms of resistance to brute force attacks.7.4.2 Digital signatures7.4.2.1 Using digital signaturesHandwritten signatures have long been used as evidence of the identity of the authorship of document content. Digital signatures can provide the same functionality as handwritten signatures, and more. For example, suppose a customer sends a trade order to a stockbroker via email and the trade turns out to be unfavorable to the customer. It is conceivable that the customer might claim that he never sent the trade order or that someone else forged the email.The broker could require the use of a digital signature to protect itself before accepting an order sent via email. In fact, digital signatures are often used in the following situations.