Signature.getInstance("SHA1WITHRSA/ISO9796-2", "BC") works but new JcaContentSignerBuilder("SHA1WITHRSA/ISO9796-2").setProvider(BC_PROVIDER) throws an exception

[kimmerin]

Hi,

I'm trying to do a signing process by using SignerInfoGenerator to create an S/MIME-message with said signing algorithm. When trying to instantiate a ContentSigner by using the JcaContentSignerBuilder I get an exception:

Caused by: java.lang.IllegalArgumentException: Unknown signature type requested: SHA1WITHRSA/ISO9796-2
    at org.bouncycastle.operator.DefaultSignatureAlgorithmIdentifierFinder.find(Unknown Source)
    at org.bouncycastle.operator.jcajce.JcaContentSignerBuilder.getSigAlgId(Unknown Source)
    at org.bouncycastle.operator.jcajce.JcaContentSignerBuilder.build(Unknown Source)

The algorithm itself seems to be supported in general, because Signature.getInstance("SHA1WITHRSA/ISO9796-2", "BC") happily returns an instance. DefaultSignatureAlgorithmIdentifierFinder doesn't contain a maping for SHA1WITHRSA/ISO9796-2. Is this intentional or can this be added? Can I in some way pass the Signature instance to the JcaContentSignerBuilder so that it doesn't need to do the lookup in DefaultSignatureAlgorithmIdentifierFinder?

[dghgit]

We'd just need the AlgorithmIdentifier that describes this one... I don't actually know if there is one though. You could allocate a proprietary one. You do need one though, CMS requires an ASN.1 definition for the algorithm in order to create the encoded message.