Cryptography & stegnography
Cryptography is the practice of securing communication and information through the use of mathematical techniques, algorithms, and protocols to protect data from unauthorized access, tampering, or alteration. It is widely used to ensure confidentiality, integrity, authentication, and non-repudiation in digital systems. Here are the main principles of cryptography:
1. Confidentiality
Confidentiality ensures that only authorized parties can access the information. This is typically achieved by encrypting the data, meaning that the data is transformed into an unreadable format unless the recipient has the proper decryption key.
2. Integrity
Integrity ensures that the data has not been altered or tampered with during transmission or storage. Cryptographic methods like hashing are used to verify that the data is consistent with the original, ensuring no unauthorized modifications.
3. Authentication
Authentication verifies the identity of users, devices, or systems to ensure that they are who they claim to be. This is often achieved using digital signatures, certificates, or password-based methods.
4. Non-Repudiation
Non-repudiation ensures that a party cannot deny the authenticity of their actions, such as sending a message or making a transaction. This is commonly accomplished through digital signatures or logging mechanisms.
Key Concepts in Cryptography
Encryption and Decryption:
Encryption is the process of converting plaintext (readable data) into ciphertext (unreadable format) using an algorithm and a key.
Decryption is the process of converting ciphertext back into plaintext using a decryption key.
Symmetric vs. Asymmetric Encryption:
Symmetric encryption uses the same key for both encryption and decryption. The key must be kept secret between the sender and receiver. Example: AES (Advanced Encryption Standard).
Asymmetric encryption uses a pair of keys—public and private. The public key is used for encryption, while the private key is used for decryption. This allows for secure communication without the need to share the secret key. Example: RSA (Rivest-Shamir-Adleman).
Hashing:
Hashing is the process of converting data (like a message or file) into a fixed-length string of characters, typically a digest. This process is one-way, meaning you can't recover the original data from the hash. Hash functions like SHA (Secure Hash Algorithm) are used to ensure data integrity.
Digital Signatures:
Digital signatures use asymmetric encryption to verify the authenticity and integrity of messages or documents. The sender "signs" the message with their private key, and the recipient can verify the signature using the sender’s public key.
Public Key Infrastructure (PKI):
PKI is a framework used to manage digital keys and certificates. It enables secure communications by allowing users to verify each other’s identities using digital certificates issued by trusted Certificate Authorities (CAs).
Cryptographic Protocols:
Cryptographic protocols are sets of rules and algorithms that govern secure communication. Examples include:
SSL/TLS for secure web browsing (HTTPS).
IPsec for secure internet protocol communication.
PGP (Pretty Good Privacy) for secure email communication.
The tools can used for cryptography is as follows :
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