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IA technical specification I'm following requires me to send:

The Digital Signature must be in the form of a null content Digitally Signed message (i.e. a PKCS#7 object containing the signature but not the data that was signed).

To my understanding, this means a detached PKCS#7 signature, is that correct?

I couldn't find any definition of what a "Null Content Digitally Signed message" is. So a PKCS#7 detached seems the closest match..

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up vote 4 down vote accepted

Yes. At the ASN.1 level, it means that the OCTET STRING field (EncapsulatedContentInfo.eContent) is omitted (it is marked OPTIONAL precisely to allow for detached signatures -- the expression "null content" in that context is new to me, the usual term being "detached signature" as you correctly infer).

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(i.e. a PKCS#7 object containing the signature but not the data that was signed)

That describes exactly what a detached signature is, a signature separated from the data which was signed.

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Thanks for the quick confirmation mikeazo, it's all I needed but I'm accepting Thomas answer for the additional useful info. – Filipe Pina Nov 16 '11 at 14:56

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