pkcs7 encryption limited by memory?

[Richard Dykiel]

Hello, I am studying how pkcs7 works in openssl, particularly for encryption (enveloped data). Except if I made a mistake, it seems that pkcs7 encryption is made in memory, hence precluding encrypting very huge files: am I right?   Say you want to envelop a file: - PKCS7_dataInit returns a BIO (p7bio) that is a BIO_f_cipher+BIO_s_mem - data is enveloped by BIO_write(p7bio, data) - PKCS7_dataFinal "steals" the memory buffer of p7bio to attach it to the p7 structure - i2d_PKCS7_bio encodes the p7 structure in asn.1: in fact ASN1_i2d_bio gets called and it works entirely in a malloced temporary memory buffer!!   So if we encode a given file, the endoded data are present twice in memory: in the p7structure, and in the asn1 temporary buffer.   What directions should I take if I want to be able to encrypt large files in pkcs7 structures? It seems to me I should rewrite some PKCS7 functions, as well as try to change the ASN1 encoding so that it can work as a BIO filter?   I'd appreciate any ideas, thanks. ________________________________ Richard Dykiel, Starburst Software 150 Baker Avenue, Concord, MA 01742 http://www.starburstsoftware.com 1-800-585-3889 ext289