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Cryptography the
FaQ
Crypto sensitive communications has been
the emphasis of Cryptography throughout much
of its history.As we will see,Cryptography, to most people, is concerned with keeping
communications private.Indeed, the protection of sensitive Information is a vital part,
this is
only one part of today’s Cryptography.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. Encryption and Decryption require the use
of some secret
information,usually referred to as a
key. Depending on the Encryption mechanism used,
the same key might be used for both Encryption and Decryption, while for other mechanisms,
the keys used for Encryption and decryption migur name to some Document.
As we move to a world where our decisions and that of others be different,
But today’s cryptography is more than secret writing, more than Encryption
and
Decryption. Authentication is as fundamental a part of our lives as privacy. We use
Authentication though out our everyday life,for instance when we sign agreements
they are communicated electronically,
we need to replicate these procedures.
Cryptography provides mechanisms for such procedures.
A Digital signature binds a document to the possessor of a particular
key,
while a digital timestamp binds a document to its creation at a particular
time.
These cryptographic mechanisms can be used to control access to a shared
disk drive,
a high security installation or to a pay-per-view TV channel.
But the field of Cryptography contains even more when we include some of the
things
Cryptography enables us to do. With just a few basic tools it is possible to build
elaborate Schemes and Protocols
which allow us to pay using Electronic Money,
to prove we know certain
information without revealing the information itself, and
to share a secret quantity in such a way that no fewer than three from
a pool of five
people (for instance)
can reconstruct the secret.
While modern Cryptography is growing
increasingly diverse,
Cryptography is fundamentally based on problems that are difficult to solve.
A problem may be difficult because its solution requires some secret
knowledge,
such as Decrypting an Encrypted message or signing some Digital
document,
or the problem may be hard because it is intrinsically difficult
to complete,
such as finding a message which produces a given Hash value.
So
as the field of Cryptography has advanced, the dividing lines for what is
and
what is not Cryptography have become blurred. Cryptography today might
be
summed up as the study of Techniques and Applications that depend on the
existence of difficult problems. A
Cryptanalyst attempts to compromise Cryptographic
Mechanisms, and Cryptology
(A
Greek word meaning “ Hidden Word”)
is the discipline of Cryptography and Cryptanalysis
combined.
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