Questions Questions About Data Hashing, And Leaks

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Hello, I am very new to this website, data leaks, hashing and code in general. Here are some questions I have. I'm new to coding and trying to get a better understanding of hashes and how they relate to things like data security. I've come across terms like hash functions, data hashes, and even cryptographic hashing, but I’m still a bit unclear on the details.

Could someone help explain the following:

1. What exactly is a hash and how does it work in programming?
2. What are the common types of hash functions (e.g., MD5, SHA-256, etc.) and how are they different?
3. What’s the difference between hashing and encryption?
4. Why are some hash functions considered insecure (e.g., MD5) while others are used for secure applications (e.g., SHA-256)?
5. How are hashes used in technologies like blockchain or digital signatures?
6. Could you share any simple coding examples to demonstrate how to generate or use hashes?

Additionally, I’ve been reading about data leaks and would like to know:

1. How do hashes help in protecting sensitive data from being exposed in data leaks?
2. What are common causes of data leaks and how do hash-related vulnerabilities contribute to them?
3. How can I check if hashed data (like passwords) is at risk of being cracked?

I would appreciate any help, advice, or resources to better understand these concepts. Thanks in advance for your time!

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[swaggs09]

Hello, I will try to explain all common info about hashes simply...
In general, hash is a fixed-size output generated from input data of arbitrary size. The result of applying a hash function is called a hash value or digest. The idea is that any input, no matter its size, can be mapped to a unique, shorter string of fixed length.
The same input will always result in the same hash.
It should be quick to compute the hash for any input.
Given a hash, it should be computationally infeasible to determine the original input.
A minor change in input should drastically change the hash (called avalanche effect).
Two different inputs should not produce the same hash (collisions should be rare).

Common types of hash functions
MD5 produces a 128-bit hash value. It was widely used but is now considered insecure due to vulnerability to collisions (where two different inputs produce the same hash).
SHA-1 produces a 160-bit hash. It is more secure than MD5 but has known vulnerabilities and is no longer recommended for secure applications.
SHA-256 is a part of the SHA-2 family, produces a 256-bit hash. It is commonly used in security applications, such as blockchain and digital signatures. It is considered secure.
SHA-3 is newer hash standard that offers even stronger security and resilience against certain types of attacks.

Hashing vs Encryption
Hashing is one-way function; the original input cannot be recovered from the hash (used for data integrity).
Encryption is two-way function; encrypted data can be decrypted back into its original form using a key (used for data confidentiality).


Why are some hash functions insecure?
MD5 and SHA-1 are considered insecure because cryptographic advances have found ways to generate collisions (two inputs producing the same hash). This undermines their ability to guarantee data integrity or security.
SHA-256 is still secure because it has no known feasible collision attacks, meaning it’s extremely hard (computationally infeasible) to generate two inputs that produce the same hash.

How Hashes are Used in Blockchain or Digital Signatures

In blockchain hashing is used to link blocks of transactions. Each block contains the hash of the previous block, which ensures that no one can modify a block without affecting the entire chain (providing data integrity and immutability).

In digital signatures hash is signed with a private key. The receiver can verify the signature using the sender’s public key and by recomputing the hash of the received data. If the hashes match, the data is authentic and has not been tampered with.

To generate hash you can use for example some modules (I use hashlib in Python):

import hashlib

# Input data
data = "Hello, world!"
# Generate MD5 hash
md5_hash = hashlib.md5(data.encode()).hexdigest()
print("MD5:", md5_hash)
# Generate SHA-256 hash
sha256_hash = hashlib.sha256(data.encode()).hexdigest()
print("SHA-256:", sha256_hash)