What hash algorithm is used in Bitcoin for proof of work?

Related questions

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4. How a password is hashed?
5. What is Blockchain hash?
6. How does Salted Hash work?
7. Is hash random?
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Tags

1. #bitcoin
2. #include
3. #based
4. #thereof
5. #widely
6. #introduced
7. #cryptonight
8. #hashing
9. #quark
10. #other
11. #blake
12. #scheme
13. #proof
14. #combinations
15. #scrypt
16. #algorithms
17. #hefty1