Why SHA-256 Is Secure

• Pre-image Resistance: It’s nearly impossible to find an input from its hash.

• Second Pre-image Resistance: It’s infeasible to find two inputs producing the same hash.

• Avalanche Effect: A small change in input drastically changes the hash output.

• High Computational Cost: Brute-forcing SHA-256 requires astronomical amounts of computation.

SHA-256 in Action

Let’s say the input is Hello, Bitcoin!.

1. Apply SHA-256:

**Input: Hello, Bitcoin!

Output: 18af8192c1c09bd51a5cc4b6074c3e8c6d52f29523d20ae993f8e7c1e26e5e0f

2. Changing even one letter results in a completely different hash:

**Input: hello, Bitcoin!

Output: b53e563b8cd3fb7b0136623f2c6b3af1b30bc5018029bdabc3f125d96c3e63db

By leveraging SHA-256, Bitcoin ensures that the blockchain remains tamper-proof and secure, providing the foundation for trust in the network.

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