SLB2

SLB2 is the format used to store the encrypted bootloaders on the device.

Structure
See [SLB2 structure]

SLB2 embedded ENC Files in PUP SPKG
On 3.50 reset, 3.60 retail:
 * second_loader.enc, size: 0xD400 bytes
 * second_loader.enp, size: 0xD400 bytes
 * secure_kernel.enc, size: 0x8400 bytes
 * secure_kernel.enp, size: 0x8400 bytes

SLB2 embedded ENC Files on PSVita eMMC
On 3.50 reset, 3.60 retail:
 * second_loader.enp_, size: 0xD400 bytes
 * second_loader.enp, size: 0xD400 bytes
 * secure_kernel.enp_, size: 0x8400 bytes
 * secure_kernel.enp, size: 0x8400 bytes

ENC file structure
The last 0x340 bytes is a footer that likely contains a signed MAC of the plaintext data.