Well, .rec file is the game that, reading the above link, is encrypted with a per-console specific key that probably is inside recrypt.sys. Keys are usually 16bytes and Nintendo encryption formats are (read
here and
here for more info):
0x010000 RSA_4096 SHA1 (Unused for 3DS) 0x200 0x3C
0x010001 RSA_2048 SHA1 (Unused for 3DS) 0x100 0x3C
0x010002 Elliptic Curve with SHA1 (Unused for 3DS) 0x3C 0x40
0x010003 RSA_4096 SHA256 0x200 0x3C
0x010004 RSA_2048 SHA256 0x100 0x3C
0x010005 ECDSA with SHA256 0x3C 0x40
Also more info about Nintendo ticket system can be read
here.
Then the decrypted game must be decrypted again with a "common key" that must stored somewhere in the system dump.
Can someone post a screenshot of the 1st bytes (at least 0x200) .sys files opened with an hex editor ?
EDIT: 0-8192 partial dump taken from one of the above posted-link is surely encrypted.