Bitcoin uses SHA-256 and RIPEMD-160 cryptographic hashes. There are many aspects of Bitcoin that use hashes and the vast majority of them use a double SHA-256 encryption.

However, in a few situations that require hashes (such as e-mail addresses), a singular SHA-256 is used in combination with a singular RIPEMD-160 hash.

These hashes, when calculated on a GPU, make it feasible to perform altcoin mining using Scrypt type hashes even on a normal PC.