One-time pad

However, in the same article it was proved that any secrecy scheme that is provably secure in this sense is equivalent to one-time pads (see Section 1.5) or even less efficient. Thus, for a while, there was no further research in this field. Besides, for most applications, one-time pads were regarded as too inefficient, because the length of the secret key, which has to be exchanged beforehand, must be at least equal to the overall length of the messages that might be sent later. Hence one continued to use other schemes in practice. 

A given ciphertext C can correspond to any plaintext message M, specifically when the key K = M C. Hence, since the K is random and is never reused, it is impossible to learn anything about M from C without the secret key. That is, the one-time pad is perfectly secure. 

A cryptographically secure pseudorandom number generator can be used to make a stream cipher by using the seed as a key and treating the generator output as a long key for a pseudorandom one-time pad. 

TNA, WO32/21200, Air Ministry, Special Signals Office (AMSSO) to the British Joint Services Mission in Washington (BJSM Washington), Top Secret Cipher Telegram, Dispatched by OTP (one-time pad, an uncrackable encryption technique), 19 June 1945. 

There are few different types of encryption methods substitution, transposition, and one-time pad cipher. One of the oldest ciphers is substitution cipher, known as Caesar cipher, which substitutes every symbol with another from its group. For example A with D, B with G, and so on. This is very easy to analyze and break with common letter statistics. Transposition cipher preserves... 

We ve all used to-do lists at one time or another, but the veteran time manager uses one with considerable zeal. Some time management books suggest elaborate prioritization schemes, multiple lists, fancy calendars, and so on. The tools of our trade will be much simpler a monthly calendar, an 8i X 11-inch lined pad of paper, and a diary or their electronic equivalents. The calendar is simply used to record aU events, appointments, and fixed-date deadlines. The pad of paper is used to track all activities, both to do and pending, as well as each day s activities. The diary is used to track who you talked to and what you did. Of course, in an age of ubiquitous personal computers and personal digital assistants, calendars, to-do lists, and diaries all have electronic counterparts. I... 

Surprisingly, M.C.Escher, the greatest graphic artist (1898-1972), probably unfamiliar with Markov processes, has already demonstrated in 1931 the same situation in his woodcut Frog [10, p.231]. This is reproduced in Fig.0-1. As time goes by, the frog, system, jumps from one lily pad, state, to another according to... 

N-8 (163 N Storage Pad) 100-N/IC Areas Solid 1,000 drums can be stored at one time 616 bldg or radioactive retrievals storage units Hazardous and low-level radioactive waste... 

Fixed rigid media are available in the forms of disks, pads and cartridges. They are composed of firm, rigid particles set in permanent contact with one another. The media formed have excellent void uniformity, resistance to wear and ease in handling as piece units. Depending on the particle size forming the filter media, temperature, pressure and time for caking, it is possible to manufacture media with... 

Following this procedure, the funnel is positioned in a padded ring in a ring stand and left undisturbed for a period of time to allow the two immiscible layers to once again separate. The purpose of the specific design of the separatory funnel is mostly to provide for easy separation of the two immiscible liquid layers after the extraction takes place. All one needs to do is remove the stopper, open the stopcock, allow the bottom layer to drain, and then close the stopcock when the interface between the two layers disappears from sight in the stopcock. The denser of the two liquids is the bottom layer and will be drained through the stopcock first. The entire process may need to be repeated several times, since the... 

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