Digital Signing guidelines - NatWest

Bankline Direct will use whatever data is between the MIME Part 1 start and end boundaries to verify the
signature. Therefore, the data that needs to be signed must include all data from MIME Part 1.
All this must be sent to the signing application:
MIME Part 1
Content-Type: {content type/content sub-type}{CRLF}
{CRLF}
{raw data}{CRLF}
For example
Content-Type: text/plain
Field1A,Field2A,Field3A
Field1B,Field2B,Field3B
Embedded Signatures
An embedded signature is where the signature and data are combined within a single (Cryptographic Message
Syntax) CMS structure. These are also known as Opaque signatures.
MIME Header
MIME Part
Signed Data and Signature – CMS format
This can be represented as follows:
MIME Header
MIME-Version: 1.0{CRLF}
Content-Disposition: attachment;
{optional CRLF}{SPACE}filename=”smime.p7m”{CRLF}
Content-Type: application/x-pkcs7-mime;
{optional CRLF}{SPACE}smime-type=signed-data;
{optional CRLF}{SPACE}name=”smime.p7m”{CRLF}
Content-Transfer-Encoding: base64{CRLF}
{CRLF}
MIME Part
{CMS object with Data and Signature}
11