Essentially, the code version of a "book cipher" is just like any other code, but one in which the trouble of preparing and distributing the codebook has been eliminated by using an existing text. However this means, as well as being attacked by all the usual means employed against other codes or ciphers, partial solutions may help the cryptanalyst to guess other codewords, or even to completely break the code by identifying the key text. This is, however, not the only way a book cipher may be broken. It is still susceptible to other methods of cryptanalysis, and as such is quite easily broken, even without sophisticated means, without the cryptanalist having any idea what book the cipher is keyed to.
If used carefully, the cipher version is probably much stronger, because it acts as a homophonic cipher with an extremely large number of equivalents. However, this is at the cost of a very large ciphertext expansion.
Read more about this topic: Book Cipher
Other articles related to "security":
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Famous quotes containing the word security:
“The contention that a standing army and navy is the best security of peace is about as logical as the claim that the most peaceful citizen is he who goes about heavily armed. The experience of every-day life fully proves that the armed individual is invariably anxious to try his strength. The same is historically true of governments. Really peaceful countries do not waste life and energy in war preparations, with the result that peace is maintained.”
—Emma Goldman (18691940)
“Is a Bill of Rights a security for [religious liberty]? If there were but one sect in America, a Bill of Rights would be a small protection for liberty.... Freedom derives from a multiplicity of sects, which pervade America, and which is the best and only security for religious liberty in any society. For where there is such a variety of sects, there cannot be a majority of any one sect to oppress and persecute the rest.”
—James Madison (17511836)
“It is hard for those who have never known persecution,
And who have never known a Christian,
To believe these tales of Christian persecution.
It is hard for those who live near a Bank
To doubt the security of their money.”
—T.S. (Thomas Stearns)