What is Cryptography?
The word "cryptography" is derived from the Greek kryptos, meaning hidden. The origin of cryptography is usually dated from about 2000 B.C., with the Egyptian practice of hieroglyphics.
Defi: "Cryptography is the process of protecting or encrypted the information and provide secure communication in the presence of third parties called adversaries, security action is perform by codes."
Features Of Cryptography:
- Confidentiality
- Integrity
- Non-repudiation
- Authentication
what is security?
And types is security attack?
Cryptographic systems are generically classified along three independent dimensions:
1. The type of operations used for transforming plaintext to ciphertext. All
encryption algorithms are based on two general principles: substitution, in
which each element in the plaintext (bit, letter, group of bits or letters) is
mapped into another element, and transposition, in which elements in the
plaintext are rearranged. The fundamental requirement is that no information
be lost (that is, that all operations be reversible). Most systems, referred to as
product systems, involve multiple stages of substitutions and transpositions.
2. The number of keys used. If both sender and receiver use the same key, the system
is referred to as symmetric, single-key, secret-key, or conventional encryption. If the
sender and receiver each use a different key,the system is referred to as asymmetric,
two-key, or public-key encryption.
3. The way in which the plaintext is processed. A block cipher processes the input
one block of elements at a time, producing an output block for each input
block. A stream cipher processes the input elements continuously, producing
output one element at a time, as it goes along.
