Earlier quoted context omitted.
Your citations proves my point, not yours. > This is because it is difficult to find a hash of x that is equal to hash of y in computationally feasible time (collision-resistance). This is exactly what I was explaining.
This is literally proof of work. I don’t know what else I can do to explain that Bitcoin’s immutability property is directly parametrized by the security level in the PoW mechanism. You are arguing that decentralization creates immutability. Decentralization has nothing to do with hashing.
Collision and proof of work are really not the same thing.
Here are some Python code that compares the two. If you're not convinced, I suggest you try using it to time what is actually harder and what makes a blockchain immutable. Then come back here when you found a collision :).
import hashlib
def h (d): return hashlib.sha256(d).hexdigest()
def mine_for_PoW (d):
nonce = 0
while True:
blk = f"{d}{nonce}".encode()
sha = h(blk)
if sha[0:6] == '000000': ## PoW
return sha, nonce
nonce += 1
def find_collision (d, original):
nonce = 0
while True:
blk = f"{d}{nonce}".encode()
sha = h(blk)
if sha == original: ## collision
return nonce
nonce += 1