Hashing

• What is Hashing? 

  • Hashing is a method to convert any data into a fixed-size string of characters 
  • This fixed-size output is often called a digest 
  • Same input will always produce the same hash, providing consistency 
  • Even a minor change in input produces a radically different hash, giving it sensitivity to data changes

  
• Hashing Examples

  
• Some common hashing algorithms are: 

  • MD5 (Message Digest 5) 
  • Widely used but considered weak due to vulnerabilities to collision attacks 
  • SHA-1 (Secure Hash Algorithm 1) 
  • Previously used in SSL certificates and software repositories, now considered weak due to vulnerabilities 
  • SHA-256 (Part of the SHA-2 family) 
  • Commonly used in cryptographic applications and data integrity checks. Considered secure for most practical purposes 
  • SHA-3 
  • The most recent member of the Secure Hash Algorithm family, designed to provide higher levels of security 
• Encryption vs Hashing

  
• Hashing for Password Storage #1 

  • Hashing is commonly used for storing passwords 
  • When the user first signs up, the password they provide is hashed 
  • The hashed password is stored in the database, rather than as plaintext 
  • When users try to log in, they enter their username and password 
  • The system hashes the password entered by the user during the login attempt 
  • The hashed password is compared against the stored hash in the database 
  • If the hashes match, the user is authenticated and granted access 
  • If they don't match, access is denied 
• Hashing for Password Storage #2

  • Hashing passwords adds an extra layer of security 
  • Even if the database is compromised, the attacker can't use the hashed passwords directly 
  • In case of a data breach, not storing passwords in plaintext minimises the risk and potential legal repercussions 
  • Users' raw passwords are not exposed, reducing the impact of a data breach 
  • Since the hash function always produces the same output for the same input, verifying a user's password is quick 
• Hashing for password storage image

  
• Why is Hashing an efficient method for data retrieval? 

  • Database lookup
  • Data integrity 
• Database lookup#1

  • A good hash function uniformly distributes keys across the hash table, allowing for a more balanced and efficient data retrieval 
  • The hashed table has no order 
  • New users are randomly inserted into the hash table, which leads to a uniform distribution 
  • If the website application needs to fetch the user's data from the table, it is computationally more efficient to query using the hash digest value than any other attribute 
• Database lookup#2

  • This is because hash digests have a fixed length, making it easier for the computer to compare hash digests rather than variable-length strings like email addresses
  • The hash digest serves as a summarised representation of the data
  • The hash digest serves as a summarised representation of the data (email address in the above example)

  
• Data integrity 

  • Another benefit of hashing data is being able to verify its integrity 
  • When data is being transferred over a network, it is susceptible to loss of packets or malicious interference, so if two hashes are compared and are identical, it allows a system to verify the integrity of data 
  • This is because the same data hashed by the same hashing function will produce the same digest 
  • Comparing two fixed-size hashes is computationally less intensive than string comparison