From: https://en.wikipedia.org/wiki/SHA-2 https://en.wikipedia.org/wiki/SHA-2 "In March 2012, the standard was updated in FIPS PUB 180-4, adding the hash funct

From: https://en.wikipedia.org/wiki/SHA-2 https://en.wikipedia.org/wiki/SHA-2 "In March 2012, the standard was updated in FIPS PUB 180-4, adding the hash functions SHA-512/224 and SHA-512/256, and describing a method for generating initial values for truncated versions of SHA-512. Additionally, a restriction on padding the input data prior to hash calculation was removed, allowing hash data to be calculated simultaneously with content generation, such as a real-time video or audio feed. Padding the final data block must still occur prior to hash output" This sounds like more than just truncating SHA-2 512. Also, the various articles on stackexchange state that there is no way to truncate SHA-2 512 and conform to SHA-2 512/256. Finally, https://eprint.iacr.org/2010/548.pdf https://eprint.iacr.org/2010/548.pdf sounds like they really wanted you to be able to distinguish SHA-512/256 from a truncated SHA-512: "In order for users to be able to distinguish between a SHA-512 digest which has been truncated and a SHA512/256 digest, we also offer new initialization constants, analogous to those used in SHA-384."