5.12. We now analyze the security of DES double encryption (2DES) by doing a cos

Question

5.12. We now analyze the security of DES double encryption (2DES) by doing a cost-estimate:

2DE S(x) = DE Sk2 (DE Sk1 (x))

1. First, let us assume a pure key search without any memory usage. For this purpose, the whole key space spanned by K1 and K2 has to be searched. How much does a key-search machine for breaking 2DES (worst case) in 1 week cost?In this case, assume ASICs which can perform 107 keys per second at a cost of $5 per IC. Furthermore, assume an overhead of 50% for building the key search machine.

2. Let us now consider the meet-in-the-middle (or time-memory tradeoff) attack, in which we can use memory. Answer the following questions:

a.     How many entries have to be stored?

b.    How many bytes (not bits!) have to be stored for each entry?

c.     How costly is a key search in one week? Please note that the key space has to be searched before filling up the memory completely. Then we can begin to search the key space of the second key. Assume the same hardware for both key spaces. For a rough cost estimate, assume the following costs for hard disk space: $8/10 GByte, where 1 GByte = 109 Byte.

3. Assuming Moore’s Law, when do the costs move below $1 million?

Explanation / Answer

Moore’s Law could be a computing term that originated around 1970; the simplified version of this law states that processor speeds, or overall process power for computers can double each 2 years. a fast check among techniciansin numerous laptop corporations shows that the term isn't highly regarded howeverthe rule continues to beaccepted.
To break down the law even any, it specifically explicit that the amount of transistors on an inexpensivemainframewould double each 2 years (which is basically constant factor that was explicit before) however ‘more
this can be as a result of we tend to square measure staring at the speeds and not the amount of transistors; in 2000 the amount of transistors within the mainframe numbered thirty seven.5 million, whereas in 2009 the amount went up to an impressive 904 million; this can be why it's a lot of correct to use the law to transistors thanto hurry.
With all this talk about transistors the typical technician or someone might not perceive what the figures mean; a less complicated thanks to make a case for is that the sooner mainframes on the market had onespeed or frequency rating whereas the newer models have a rating that refers to over one CPU.
If you’ve purchased a laptop recently you would possibly} have a concept of what this implies as salespersons may have oversubscribed you on the wonders of multi-core CPUs. within the example given higher than, the speeds over an oversized variety of years went between one.3 and 2.8, that is barely double however what mustbe unbroken in mind is that the two.8 could be a QUAD CORE whereas the one.3 could be a single CORE. this implies that the particular power of the two.8 would be found if you multiply by four – which might provide you with a walloping eleven.2 that could be a way cry from one.3.
Due to the speedy rate that technology has full-grown within the past few years, most laptop technicians you speak with – whether or not they have detected of Moore’s Law or not can tell you that mainframespeeds doubleevery year. tho' Moore’s Law had aforesaid each 2 years, this speedy increase in technological production has lessened the amount within the minds of technicians and users alike.
The limitation that exists is that when transistors may be created as little as atomic particles, then there'llbe no a lot of space for growth within the mainframe market wherever speeds square measure involved

Related Questions

Navigate

• Browse (All)
• Browse 5
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.