An AES-encrypted secret storage payload. See https://spec.matrix.org/v1.11/client-server-api/#msecret_storagev1aes-hmac-sha2-1
the ciphertext in base64
the initialization vector in base64
the HMAC in base64
An AES-encrypted secret storage payload. See https://spec.matrix.org/v1.11/client-server-api/#msecret_storagev1aes-hmac-sha2-1