Convert::X509::minipkcs7 - parse pkcs7 messages just to get only SN list of recipients/signers and correspondent crypto-algorithmes
use Convert::X509::minipkcs7; use Data::Dumper; open(F,'<', $ARGV[0]) or die; binmode(F); local $/; my $data=Convert::X509::minipkcs7->new(<F>); print Dumper($data->snlist());