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What is this special attribute added to PKCS#12 files to make MS software import keys as signature only?

April 26, 2017added files import keys MS pkcs#12 Software special

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What is this special attribute added to PKCS#12 files to make MS software import keys as signature only?

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A. When I closely analysed MS PKCS#12 files used for signing only and key exchange I noticed that the PKCS#8 PrivateKeyInfo structure contained a keyUsage attribute. The object identifier is the same as the keyUsage certificate extensions and the associcated parameter is a BITSTRING. A signature key has the digitalsignature bit set and an exchange key has the dataEncipherment bit set. This corresponds to bits 0 and 3 or the values 0x80 and 0x10 respectively.