Please note that, you don't have to use a BLOB with the API you are referring to because it is not needed. It is not needed because you already know the Enrollment ID. The Enrollment ID is used to obtain the token, therefore there is no need to create another.
Please click or navigate to the link below for a BLOB description. I also included the BLOB description below.
"BLOB field (URL safe base 64 encoded) that represents the encrypted payload for payment instrument. (See Encrypted Payment Instrument). Format: JSON Web Encryption using shared secret made available at time of onboarding. Encrypted Blob of all Payment instrument details. Payment instrument contains: accountNumber, cvv2, last4, name, billingAddress, expirationDate. Please see the note below regarding internationalization support for encPaymentInstrument."
Please note: In the BLOB description above, it also states that additional information will be made available at the time of on-boarding.