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wdw

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  1. [studiu interesant] Time and energy required to brute-force a AES-256 encryption key

    in Off-topic

    Posted

    I did a report on encryption a while ago, and I thought I'd post a bit of it here as it's quite mind-boggling.

    AES-256 is the standardized encryption specification. It's used worldwide by everyone from corporations to the US government. It's largest key size is 256 bits. This means that the key, the thing that turns encrypted data into unencrypted data, is string of 256 1s or 0s.

    With each character having two possibilities (1 or 0), there are 2256 possible combinations. Typically, only 50% of these need to be exhausted to yield the correct key, so only 2255 need to be guessed. How long would it take to flip through each of the possible keys?

    When doing mundane, repetitive calculations (such as brute-forcing or bitcoin mining), the GPU is better suited than the CPU. A high-end GPU can typically do about 2 billion calculations per second (2 gigaflops). So, we'll use GPUs.

    Say you had a billion of these, all hooked together in a massively parallel computer system. Together, they could perform at 2e18 flops, or 

     2 000 000 000 000 000 000 keys per second (2 quintillion)

    1 billion gpus @ 2 gigaflops each (2 billion flops)

    Since there are 31 556 952 seconds in a year, we can multiply by that to get the keys per year. 

      *31 556 952
  =6.3113904e25 keys per year (~10 septillion, 10 yottaflops)

    Now we divide 2255 combinations by 6.3113904e25 keys per year: 

     2^255 / 6.3113904e25

 =9.1732631e50 years

    The universe itself only existed for 14 billion (1.4e10) years. It would take ~6.7e40 times longer than the age of the universe to exhaust half of the keyspace of a AES-256 key.

    On top of this, there is an energy limitation. The The Landauer limit is a theoretical limit of energy consumption of a computation. It holds that on a system that is logically irreversible (bits do not reset themselves back to 0 from 1), a change in the value of a bit requires an entropy increase according to kTln2, where k is the Boltzmann constant, T is the temperature of the circuit in kelvins and ln2 is the natural log(2).

    Lets try our experiment while considering power.

    most high-end GPUs take around 150 watts of energy to power themselves at full load. This doesn't include cooling systems. 

     150 000 000 000 watts (150 gigawatts)

    1 billion gpus @ 150 watts 

     1.5e11 watts

    This is enough power to power 50 million american households.

    The largest nuclear power reactors (Kashiwazaki-Kariwa) generate about 1 gigawatt of energy. 

     1.5e11 watts / 1 gigawatt = 150

    Therefore, 1 billion GPUs would require 150 nuclear power plant reactors to constantly power them, and it would still take longer than the age of the universe to exhaust half of a AES-256 keyspace.

    1 billion GPUs is kind of unrealistic. How about a supercomputer?

    The Tianhe-2 Supercomputer is the world's fastest supercomputer located at Sun Yat-sen University, Guangzhou, China. It clocks in at around 34 petaflops.

    Tianhe-2 Supercomputer @ 33.86 petaflops (quadrillion flops) 

     =33 860 000 000 000 000 keys per second (33.86 quadrilion)

 3.386e16 * 31556952 seconds in a year

    2255 possible keys 

     2^255 / 1.0685184e24

 =1.0685184e24 keys per year (~1 septillion, 1 yottaflop)

 =5.4183479e52 years

    That's just for 1 machine. Reducing the time by just one power would require 10 more basketball court-sized supercomputers. To reduce the time by x power, we would require 10x basketball court-sized supercomputers. It would take 1038 Tianhe-2 Supercomputers running for the entirety of the existence of everything to exhaust half of the keyspace of a AES-256 key.

     

    SURSA

    • Upvote 2

  2. Am I hacked? Oh, it's just Vodafone

    in Stiri securitate

    Posted · Edited by wdw
    added some shit

    Asta se intampla pt ca Vodafone(de fapt fiecare serviciu de telefonie) are o utilitara pentru web cache, cum af fi squid, pentru a reduce din traficul lor, servind fisiere stocate la ei pe servere. Binenteles ca treaba este valabila doar pt conexiuni in plain (http?) si nu si pt cele encriptate(https/vpn samd)

    Edit: partea buna e ca-ti mai salveaza si tie din trafic

  7. Securizarea conexiunii SSH

    in Tutoriale in romana

    Posted · Edited by wdw
    formatare

    Bune sfaturi. Îns?...

    1. la pasul 2, se comenteaza linia respectiva sau se seteaza no

    2. ar trebui sa se foloseasc? certificate, nu parole

    3. schimbarea portului nu e o idee (chiar) buna (si in general, toate practicile de tip „security through obscurity„) - vezi aici de ce ?i ce practici alternative se recomand?.

  8. Kali nu functioneaza dupa upgade

    in Sisteme de operare si discutii hardware

    Posted

    pff... ai bagat repos pentru debian. de aia e bine sa-ti faci periodic backupuri la partitiile importante... asa inveti :)) ; e dureros dar bagi la cap...

    intra in recovery mode, scoate sursele care nu au ce cauta acolo si incearca un upgrade / dist-upgrade, sau eventual uita-te prin loguri sa vezi ce s-a instalat recent, scoate-le si baga-le iar cu sursele oficiale; nu iti garantez ca merge dar merita incercat

  23. [ebook] Black Hat Python: Python Programming for Hackers and Pentesters [Python 2.x]

    in Free stuff

    Posted

    Brief contents


    Chapter 1: Setting Up Your Python Environment
    Chapter 2: The Network: Basics
    Chapter 3: The Network: Raw Sockets and Sniffing
    Chapter 4: Owning the Network with Scapy
    Chapter 5: Web Hackery
    Chapter 6: Extending Burp Proxy
    Chapter 7: GitHub Command and Control
    Chapter 8: Common Trojaning Tasks on Windows
    Chapter 9: Fun with Internet Explorer
    Chapter 10: Windows Privilege Escalation
    Chapter 11: Automating Offensive Forensics
    Index

    www.mediafire.com/download/r3g1pef6ccsbplc/Black.pdf

  25. Black Fraier Day

    in Off-topic

    Posted

    Daca tot venii vorba de black friday si vreti sa mergeti sa cumparati haine din H&M Zara Pull&Bear Bershka etc....

    Ma contactati pe mine si va dau eu tot ce doriti la un pret foarte bun If you know what i mean ;)

    Sunt dn CJ

    P:S Nu ma injurati si vedeti-va de treaba voastra :))

    vii la vara in Constanta? :))

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