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The science and art of manipulating messages to make them secure is called
cryptography.
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Original message to be transformed is called plaintext.
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Resulting message after the transformation is called ciphertext.
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Process of converting plaintext to ciphertext is called encryption
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Reverse process is called decryption
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Algorithm used for encryption and decryption is called Cipher.
Ex
: Substitution and Transposition Ciphers Substitution Cipher
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Substitution ciphers are a common technique for altering messages in games and
puzzles.
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Each letter of the alphabet is mapped into another letter.
a b c d e f g h i j k l m
n o p q r s t u v w x y z
z y x w v u t s r q p o n
m l k j i h g f e d c b a
Transposition
Cipher :
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Here the order in which the letters of the message appear is altered.
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Substitution and transposition techniques are easily broken.
Cryptographic
method must meet several requirements
1.
It must be easy to implement
2.
It should be deployable on large scale
3.
It must provide security to all of its users.
4.
It should prevent an attacker from deriving the key even when a large sample of
the plaintext and corresponding ciphertext is known
Cryptography
is best known as a way of keeping the contents of a message secret.
Confidentiality
of network communications, for example, is of great importance for ecommerce and
other network applications.. In particular, cryptography allows the network business
and customer to verify the authenticity and integrity of their transactions. If
the trend to a global electronic marketplace continues, better cryptographic
techniques will have to be developed to protect business transactions.
Cryptography
is best known as a way of keeping the contents of a message secret.
Confidentiality
of network communications, for example, is of great importance for ecommerce and
other network applications.. In particular, cryptography allows the network business
and customer to verify the authenticity and integrity of their transactions. If
the trend to a global electronic marketplace continues, better cryptographic
techniques will have to be developed to protect business transactions.
Sensitive
information sent over an open network may be scrambled into a form that cannot be
understood by a hacker or eavesdropper. This is done using a mathematical
formula, known as an encryption algorithm, which transforms the bits of the
message into an unintelligible form. The intended recipient has a decryption
algorithm for extracting the original message. There are many examples of
information on open networks, which need to be protected in this way, for
instance, bank account details, credit card transactions, or confidential health
or tax records.
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