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Significance of Random Numbers in Cryptography


Random numbers are crucial for cryptography and secure communications. Read on to know why random numbers is crucial secure digital communication…

Random numbers, which are unpredictable and hard to guess, are crucial for cryptography and secure communications. Creating a truly random number, or a set of random numbers, is surprisingly difficult.

One of the common instance where random numbers is crucial for secure digital communication is the case of One-Time Password (OTP). All of us are familiar with the OTPs which we reveive on the mobile phone and email for various digital transactions. If those OTPs were predictable, financial transactions would not be secure. Random numbers are essential for most forms of cryptography. In fact, “Randoms” are also vital for many scientific and social experiments. For instance, medical trials and opinion polling require random sampling. Monte Carlo methods of testing investment strategies, or running physics experiments, also rely on random numbers.

Random Numbers
If you could actually guess random numbers, you could decode several forms of encryption and networks would become insecure. Most modern encryption methods rely on using a long random number or sequences of long random numbers as the key. And that number itself may have been generated using another random number. Then, a large random number is chosen as a “seed”. That seed is run through various mathematical operations such as multiplied and divided by other numbers — for instance to generate a new number, which is then used as a key for an encryption system. One of the challenge in this process is that it’s quite hard to generate a seed, which is entirely random and unpredictable. Computers are brilliant at doing repetitive tasks, which actually makes it hard for them to generate a string of new, entirely random numbers on demand. It’s also possible, even likely, that a codebreaker will know or understand the cryptographic procedure in use.

Public Key Encryption
In systems, such as the popular Public Key Encryption (PKE), the cryptographic algorithm is known to everybody and the message transmitted is often in the public domain. This is also the case with peer-to-peer processing of Bitcoin transactions. Everybody understands the algorithm in use. And yet, it is very difficult to forge a transaction or to understand a public key encryption message because every user uses a private key.

Programmers have found ingenious ways to get around the limitations of computers by finding strange ways to generate random numbers. One of the most elegant methods involves the use of lava lamps — those decorative artefacts with coloured liquids flowing inside them.

Lava Lamps & Random Numbers
Cloudflare is a major DNS service provider and t processes around 10 per cent of the Internet’s traffic. It must protect its own traffic and also provide security against hackers and Denial of Service attacks to its many clients. This means that it needs to generate a constant stream of large random numbers. Cloudflare uses a wall of about 100 lava lamps in its San Francisco office to generate the seeds.

The mechanics of these devices are simple. Pick two insoluble liquids such as various oils and these must have different colours but similar density and viscosity. Put the liquids into a transparent container with an electric bulb at the bottom. The bulb heats the liquid, which rises and is replaced by cooler liquid from the top. In turn, this liquid is heated and rises, etc. This process creates unpredictable random patterns, which look like volcanic lava flows.

Now, every digital image is recorded, pixel by pixel, as a string of numbers. So pictures of that Cloudflare wall automatically become long random numbers!

Other Random Number Generation Process
There are other less aesthetic methods of generating seeds. For instance, some systems use the decimal points of local temperature, or the computer’s internal temperature. Other methods use natural, unpredictable phenomena like the exact durations of earthquakes, or the exact moments at which a tremor was recorded.

This is one of the wonderful paradoxes of modern technology. Having designed machines to predictably and accurately perform the same tasks again and again, we protect these machines by finding numbers that are as unpredictable as possible.


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