The problem SoulShip solves

NFTs today are used for their financial value rather than their use cases which include event passes, identities, degrees, etc.

The ERC721 and ERC1155 NFT standards are not capable of serving these use cases since their ownership can be transferred which makes it unusable to be used for identity or degree, etc
We need a standard which does not permit the users to transfer the ownership of their NFTs. These tokens have to be attached to the address it is minted to.

We are bringing forward the actual value of NFTs by creating an SBT token standard. Also with permission-based minting model, spamming of tokens can also be avoided. The permission is granted using an EIP712 signature.
Check the thread on Ethereum Magicians Forum - https://ethereum-magicians.org/t/eip1705-an-account-bound-token-with-permission-based-minting/10526

Since the permission is granted using signatures, it is totally gasless and avoids spamming by allowing the user to exercise control over the minting process.
Also, we have another parameter called validity, along with the signature. The values of this parameter can be one-time or forever.
The receiver can grant the forever validity to trusted contracts and then it won't have to ask for the user's signature ever again for minting tokens.

Challenges we ran into

Since the permission is granted using the EIP712 signature, we thought of implementing a validity to the signature. The signature will be valid for either one-time use or forever.

We wanted to encode the validity data along with the signature but we faced a big technical challenge with decoding the validity parameter from the signature on-chain.
Since EIP712 signatures can only be ec-recovered on-chain, only the signer address can be retrieved.