IPFS is a peer-to-peer hypermedia protocol mainly used as a decentralized file system. In order to exploit the possibilities of an open certification platform we have integrated IPFS at the smart contract level: each certificate has optional IPFS reference to the original document and certificate data.
In the same way the entity data and all the public details from its signers is publicly stored in IPFS and referenced within the smart contract itself. In this way the data integrity is guarnateed since any change in the referred would result a different IPFS multihash.
At the moment IPFS integrity is one of the provided servides by Ethertify's website and not at contract level. Nonetheless future contract extensions will allow IPFS integrity verification at contract level.