1.0-cryptography.md

Cryptography

Cryptography is the science of encoding information.

Cryptographic Mechanisms

• Primitives:
  • mathematical operations used as building blocks in the realization of schemes;
  • e.g. DES, AES, RSA, ECC, etc;
• Schemes:
  • combination of primitives and additional methods for the realization of cryptographic tasks such as cipher and digital signature;
  • e.g. DES-CBC-PKCS5Padding, RSA-OAEP, etc;
• Protocols:
  • sequences of operations performed by one or more entities, involving schemes and primitives;
  • e.g. TLS, TLS_RSA_WITH_AES_128_CBC_SHA, etc.

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Scheme Types

Schemes can be classified in two main groups:

Symmetric Schemes

• Cypher and authentication;
• Secret key used by both parties (cipher and decipher);
• Used to generate and verify the MAC;
• e.g. DES, AES, etc;
• Faster, but not so safe;

Asymmetric Schemes

• Cypher and digital signature;
• Public key to cipher and private key to decipher;
• Cypher schemes - "Everyone can cipher, only the receiver can decipher";
• Authentication schemes - "Everyone can verify, only the authorized sender can sign";
• Safer, but slower;

	Symmetric	Asymmetric
Confidentiality	Symmetric Cipher	Asymmetric cipher
Authenticity	MAC	Digital Signature

The difference between the MAC and the digital signature schemes are the following:

	MAC	Digital Signature
Integrity	Yes	Yes
Authenticity	Yes	Yes
Non-repudiation	No	Yes
Speed	Fast	Slow
Security	Low	High
Key	Secret	Public/Private
Complexity	Low	High