A safekeeping account is an account (generally a record in a book-entry system) maintained by an account servicer on behalf of an account owner, with the purpose of holding traditional securities.
A cash account is an account (generally a record in a book-entry system) maintained by an account servicer on behalf of an account owner, with the purpose of recording all cash-related transactions, notably cash receipts and payments.
A crypto account is a concept proposed under the CAST Framework designed to encompass the public cryptographic key, the private cryptographic key and the public address of a given holder of Security Tokens or other kinds of Digital Assets. A crypto account is provided by a crypto servicer to a crypto owner or generated by the crypto owner itself, for the purpose of holding Security Tokens or other kinds of Digital Assets for a specific DLT. Unlike a safekeeping or cash account, it is not a record in a book-entry system, but it is based on a (cryptographic) private key whose detention acts as a proof of ownership. A public key is derived from the private key which in turn is derived into a public address. This public address can be considered as the account number of the crypto account.
A wallet is a storage solution for private keys. By extension, a wallet is a safekeeping solution for crypto accounts.
A custodial wallet is a wallet where private keys are provisioned and stored by a third-party (the Crypto-Asset Service Provider).
SSI (“Standard Settlement Instructions”) are settlement instructions that have been agreed in advance. They serve as a reference for transaction settlement, indicating the default securities and/or cash accounts to be used.
Crypto SSI are equivalent to SSI. They indicate the default crypto accounts to be used for transaction settlement involving tokens. They can include default cash accounts to be used if the payment leg of a transaction is settled in traditional cash.