The blockchain is an emerging technology. It is widely used because of its efficiency and functionality. The hash function, as a supporting aspect of the data structure, is critical for assuring the blockchain’s availability and security. Hash functions, which were originally designed for use in a few cryptographic schemes with specific security needs, have since become regular fare for many developers and protocol designers, who regard them as black boxes with magical characteristics. Message digesting, password verification, data structures, compiler operation and linking file name and path together are contemporary examples of hash functions applications. Since 2004, we’ve observed an exponential increase in the number and power of attacks against standard hash algorithms. In this paper, we investigated reported security flaws on well-known hashing algorithms and determined which of them are broken. A hash function is said to be broken when an attack is found, which, by exploiting special details of how the hash function operates, finds a preimage, a second preimage or a collision faster than the corresponding generic attack. To increase background knowledge, we also provide a summary of the types of attacks in this area. Finally, we summarized the information of the broken hash algorithms in a table which is very helpful for selecting, designing or using blockchains
