I have an application which needs to do encryption and decryption of
files which may not fit in main memory. I'm using the PKCS#7
enveloped-data format, and have implemented the encryption side of
things using Steve Henson's work as a reference:

  <http://cvs.openssl.org/chngview?cn=15749>

Don't worry Steve, I'm not actually using 0.9.9, I just used it as a
reference for my own implementation. (Basically, I implemented the
smallest subset of indefinite length encoding necessary for PKCS#7
enveloped-data.)

Now it's time to implement streaming decryption. I've got it working via
d2i_PKCS7() and PKCS7_decrypt(), but of course that requires the entire
encoded data be in memory. As far as I can see, there's no support in
either 0.9.8 or 0.9.9 for streaming decryption, so I'm without a
reference this time. I think the right approach is to build up my own
PKCS7 structure by using ASN1_d2i_bio() on the individual parts, and
then use PKCS7_dataDecode(), passing my own read BIO. Does that sound
right?

Thanks,
John
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