Danni-Tech

Key Points from This Video on Hashing:

• What is Hashing?
  Hashing is the process of using a mathematical algorithm to produce a numeric value (digest) that represents the original data. This is often referred to as a fingerprint, digest, or simply a hash.

• Simple Example of Hashing:

  • The word “friend” is hashed, with each letter represented by its alphabetical position, resulting in a numeric value of 56.
  • Even a small change (e.g., removing a letter to form “fried”) results in a completely different hash value, such as 42, demonstrating how hashes detect data changes.

• Purpose of Hashing:
  Hashing is commonly used to verify data integrity by detecting changes in the original data.

• Collisions in Hashing:

  • A collision occurs when two different inputs produce the same hash value.
  • Collisions are unavoidable because hash functions generate a fixed-size digest, which limits the number of possible outputs.

• Example of a Collision:

  • Using a simple 2-bit hashing algorithm (SimpleHash2), there are only 4 possible outputs: 00, 01, 10, 11.
  • With more inputs than outputs, different messages will eventually share the same hash, causing a collision.

• Common Hashing Algorithms:

  • MD5 – 128-bit digest
  • SHA-1 – 160-bit digest
  • SHA-224 – 224-bit digest
  • SHA-384 – 384-bit digest
  • SHA-512 – 512-bit digest

• Demonstration Using Linux (Ubuntu via WSL):

  • The echo command is used to send data to standard output:
    echo "friend"
  • Data can be hashed using utilities like sha224sum:
    echo "friend" | sha224sum
  • To avoid adding a newline character, use the -n flag:
    echo -n "friend" | sha224sum

• Key Observations from the Demo:

  1. Hashes are irreversible – You cannot determine the original message from the hash.
  2. Small changes produce drastically different hashes – Even a tiny modification alters the entire digest.
  3. Fixed-length output – Regardless of the input size, the hash output is always a fixed length.