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Encryption
is the transformation of data into some unreadable form. Its purpose is to ensure privacy by keeping the information hidden from anyone for whom it is not intended, even those who can see the encrypted data. Decryption is the reverse of encryption ; it is the transformation of encrypted data back into some intelligible form. |
| One easy
method to encrypt the alphabet is to shift the letters a fixed number
of places. For example you could encrypt A,
the first letter of the alphabet, to f the sixth letter, and B to the seventh letter g. Here we are shifting the letters five places.To make the calculations easier we use a cipher wheel. |
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To make a cipher wheel take the two wheels shown in the diagram. Place wheel one on top of wheel two so that the letters match up. To encrypt a shift of 5 places rotate wheel two 5 places. The encryption key is said to be the number of places you rotate the outer wheel, that is 5. In general such
codes are easy to break. However they can be strengthened by, say,
using four wheels instead of two, |
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| To encrypt
the first letter of the message you locate it on the first wheel and encrypt
it to the corresponding letter on the second wheel. For the second letter
of the message you use wheels two and three and wheels three and four
for the third letter. The fourth letter of the message is encrypted using
wheels one and two, etc.
In Encryption 2,
starting from their original positions, we have rotated wheel two 5
places, wheel three 12 places and wheel four 14 places. To encrypt ABRACADABRAA,
A is encrypted to f, B is
encrypted to i, R is encrypted to
t, A is encrypted to f, C
is encrypted to j etc. In this cipher the encryption key is the
numbers 5, 12, 14. |
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| This
cipher was invented by Thomas Jefferson, third president of the USA. At
times he used anything up to 26 wheels.
DID YOU KNOW that
on 3/9/96 researchers at Cray Research found a new prime number. It
is 21257787 - 1 and has 378,632 digits. |
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