The document provides an overview of hash functions and digital signatures, detailing their definitions, properties, and applications in information security. Hash functions convert inputs into fixed-size strings ensuring data integrity, while digital signatures verify authenticity and prevent tampering using public key cryptography. Both are essential for secure communication and data protection in various applications including email, legal documents, and cryptocurrency.

2. Hash Functions , Digital Signature
Subject: Information Security
Presented by: Najam

3. Introduction to Hash Functions
• Definition: A hash function is a mathematical
algorithm that converts an input (message)
into a fixed-size string of characters, which
appears random.
• Purpose: Ensures data integrity.
• Used in digital signatures and password
storage.

4. Properties of Hash Functions
• Deterministic: The same input always
produces the same hash.
• Fast Computation: Quick to generate hash
values.
• Pre-image Resistance: Difficult to reverse the
hash to the original input.
• Collision Resistance: Two different inputs
should not produce the same hash.

5. Popular Hash Functions
• MD5: Older, less secure. (not reversible)
• SHA-1: More secure but outdated.
• SHA-256: Widely used, secure.
• bcrypt: Slow, ideal for password hashing
Use this link to convert hash value
https://www.fileformat.info/

6. Qualities of Hash Function
• Fixed size hash value
• Output is unique for every input
• Hash value is irreversible
• Hashing is used to store data in database
• Password store in memory in Hash value

7. Example of Hash
Original text A
Original bytes 41 (length=1)
Adler32 00420042
CRC32 d3d99e8b
Haval 7a68154ed7868a95d5ed9dfd5f21f6d1
MD2 08e2a3810d8426443ecacaf47aeedd17
MD4 d5ef20eeb3f75679f86cf57f93ed0ffe
MD5 7fc56270e7a70fa81a5935b72eacbe29
RipeMD128 36ba1f0c642cafd7950387ecda08c467
RipeMD160 ddadef707ba62c166051b9e3cd0294c27515f2bc
SHA-1 6dcd4ce23d88e2ee9568ba546c007c63d9131c1b
SHA-256 559aead08264d5795d3909718cdd05abd49572e84fe55590
eef31a88a08fdffd
SHA-384 ad14aaf25020bef2fd4e3eb5ec0c50272cdfd66074b0ed037
c9a11254321aac0729985374beeaa5b80a504d048be1864
SHA-512 21b4f4bd9e64ed355c3eb676a28ebedaf6d8f17bdc365995
b319097153044080516bd083bfcce66121a3072646994c84
30cc382b8dc543e84880183bf856cff5

8. Introduction to Digital Signatures
• Definition: A digital signature is a cryptographic
method to verify the authenticity and integrity
of a digital message or document.
• Purpose: Ensure data authenticity.
• Verify the sender's identity.
• Prevent tampering or forgery.
• Key Concept: Uses public key cryptography for
secure signing and verification.

10. How Digital Signatures Work
• Signing Process:Sender hashes the document.
• Encrypts the hash using their private key
(creating the digital signature).
• Verification Process:Receiver decrypts the
signature using the sender’s public key.
• Compares the hash of the received document
with the decrypted hash.

11. Applications and Benefits
• Applications:
• Secure email communication.
• Legal document signing (e.g., contracts).
• Software distribution.
• Blockchain and cryptocurrency.
• Benefits:
• Prevents fraud and tampering.
• Ensures non-repudiation.
• Builds trust in digital transactions.