Ngoja tupate hekima ya mwanafilosofia Al Kindi (800-873AD) wa mji wa Baghdad ya Kale ya Babylon (Iraq) alivyoweka msingi wa kuweza kutegua ''ujumbe'' wowote wa siri kwa kulenga ujuzi wa herufi kusimamia namba au namba kuchukua nafasi za alphabeti pia kwa kutazama mfano lugha lengwa ktk ''ujumbe-siri'' herufi ''e'' hurudiwa mara ngapi katika maneno ya Kiingereza na pia herufi zingine hurudiwa mara ngapi(frequency/wingi) ktk maneno ya Kiingereza ili kubaini ''siri''. Pia ujuzi wa Anthropological linguistics kubaini ujumbe-siri umeandika ktk ''lugha gani'' ni nyenzo mojawapo ya kutengua kitendawili ktk ujumbe-siri.
Ukipenda pia kwa maelezo hapo juu kama mwandishi wa ujumbe-siri alitumia lugha ya Kiswahili, unaweza kuangalia katika lugha ya Kiswahili kila herufi hujirudia mara ngapi (wingi/frequency) katika maneno ya Kiswahili ili kubaini neno gani limefichwa ktk ujumbe-siri..
Pia kutumuia hisabati kuweza kutegua ''ujumbe'' wa siri kwa kusoma kwa kufuata mfumo fulani, fomula, frequency/wingi, kusoma kinyume nyume n.k Source:
Cracking codes | plus.maths.org
How codes became unbreakable
The technique used to crack the code is
frequency analysis: If the cipher is a simple substitution of symbols for letters, then crucial information about which symbols represent which letters can be gathered from how often the various symbols appear in the ciphertext. This idea was first described by the Arabic philosopher and mathematician Al-Kindi, who lived in Baghdad in the ninth century.
Secret Keys and One-Time Pads
In cryptography, every advance in code-breaking yields an innovation in code-making. Seeing how easily the
Equatorie code was broken, what could we do to make it more secure, or
stronger, as cryptographers would say? We might use more than one symbol to represent the same plaintext letter. A method named for the sixteenth-century French diplomat Blaise de Vigenère uses multiple Caesar ciphers. For example, we can pick twelve Caesar ciphers and use the first cipher for encrypting the 1st, 13th, and 25th letters of the plaintext; the second cipher for encrypting the 2nd, 14th, and 26th plaintext letters; and so on.
Figure 5.5 shows such a Vigenère cipher. A plaintext message beginning SECURE... would be encrypted to produce the ciphertext
llqgrw..., as indicated by the boxed characters in the figure—S is encrypted using the first row, E is encrypted using the second row, and so on. After we use the bottom row of the table, we start again at the top row, and repeat the process over and over.
Harvard University Archives.
Although this looks like gibberish, it contains some patterns that may be clues. For example, certain symbols occur more frequently than others. There are twelve
s and ten
s, and no other symbol occurs as frequently as these. In ordinary English texts, the two most frequently occurring letters are E and T, so a fair guess is that these two symbols correspond to these two letters.
Figure 5.2 shows what happens if we assume that
= E and
= T. The pattern
appears twice and apparently represents a three-letter word beginning with T and ending with E. It could be TIE or TOE, but THE seems more likely, so a reasonable assumption is that
= H. If that is true, what is the four-letter word at the beginning of the text, which begins with TH? Not THAT, because it ends with a new symbol, nor THEN, because the third letter is also new. Perhaps THIS. And there is a two-letter word beginning with T that appears twice in the second line—that must be TO. Filling in the equivalencies for H, I, S, and O yields
Figure 5.3.
Figure 5.5 A Vigenère cipher. The key,
thomasbbryan, runs down the second column. Each row represents a Caesar cipher in which the shift amount is determined by a letter of the key. (Thomas B. Bryan was an attorney who used this code for communicating with a client, Gordon McKay, in 1894.)
READ MORE:
Historical Cryptography | Secret Bits: How Codes Became Unbreakable | InformIT