Bloom filters are data structure, in the same category as hashtable and trees. They need a "hash" function to select an index for an item. A hash function in t

Bloom filters are data structure, in the same category as hashtable and trees. They need a "hash" function to select an index for an item. A hash function in that context does not need to be cryptographic, it only needs to be quick and gives a good distribution of data. SHA1 is slow, compared to a general purpose hash functions (typically murmurhash for bloom filters).