Introduction to Cryptography
(Module-3.B)
Course Code: 20B12CS332
Dr. Charu Gandhi
, Cryptography
• Cryptography is the art and science of concealing
meaning.
• Two Greek words meaning "secret writing" also
known as encryption.
• A transformation which makes data difficult for an
outsider to interpret.
• Well-disguised data made difficult to be read,
modified, or fabricated.
• Cryptography conceals data against unauthorized
access.
• Cryptanalysis is the breaking of codes.
• Cryptology: Cryptography+Cryptanalysis
, Message attacks
A message sent from sender to a receiver through a transmission medium
can be attacked by an outsider in following ways:
• Blocking: Preventing its reach the receiver , affecting the availability of
the message
• Interception : Reading or listening to the message, affecting the
confidentiality of the message
• Modification :Seizing the message and changing it in some way, affecting
the message’s integrity
• Fabrication: Sending an authentic-looking message and arranging for it to
be delivered as if it came from Sender, affecting the integrity of the
message
Encryption is a technique that can address all these problems. It is a means of
maintaining secure data in an insecure environment.
, Terminology
• Plaintext: The original form of a message is known as
plaintext.
• Key: A random data.
• Encryption: The process of encoding a message so that
its meaning is not obvious.
• Ciphertext: The encrypted form of plaintext.
• Decryption: The reverse process, transforming an
encrypted message back into its normal, original form.
(Module-3.B)
Course Code: 20B12CS332
Dr. Charu Gandhi
, Cryptography
• Cryptography is the art and science of concealing
meaning.
• Two Greek words meaning "secret writing" also
known as encryption.
• A transformation which makes data difficult for an
outsider to interpret.
• Well-disguised data made difficult to be read,
modified, or fabricated.
• Cryptography conceals data against unauthorized
access.
• Cryptanalysis is the breaking of codes.
• Cryptology: Cryptography+Cryptanalysis
, Message attacks
A message sent from sender to a receiver through a transmission medium
can be attacked by an outsider in following ways:
• Blocking: Preventing its reach the receiver , affecting the availability of
the message
• Interception : Reading or listening to the message, affecting the
confidentiality of the message
• Modification :Seizing the message and changing it in some way, affecting
the message’s integrity
• Fabrication: Sending an authentic-looking message and arranging for it to
be delivered as if it came from Sender, affecting the integrity of the
message
Encryption is a technique that can address all these problems. It is a means of
maintaining secure data in an insecure environment.
, Terminology
• Plaintext: The original form of a message is known as
plaintext.
• Key: A random data.
• Encryption: The process of encoding a message so that
its meaning is not obvious.
• Ciphertext: The encrypted form of plaintext.
• Decryption: The reverse process, transforming an
encrypted message back into its normal, original form.
