Index.dat

Location
vs0:vsh/etc/index.dat

Unpacking
contains content similar to version.txt about firmware version/build/date etc. and can be unpacked with undat (you´ll need the index.dat keys for it) - it is heavy used in MFW's for the PS3 to spoof the Firmware version.

The keys are public known in aes example papersheets : and alot others
 * "The Laws of Cryptography: Test Runs of the AES Algorithm" 2002
 * "Applied cryptography and network security" 2003

Alternative Readout
This info can also be read with More System Information

Tools
Vita .dat Tool

Example
Sample: [PSTV 3.52]

3.61 RETAIL/CEX
release: build: CEX security-repository-path: security-revision: sys-repository-path: sys-revision: sdk-internal-build-number: vsh-repository-path: vsh-revision: vsh-build-number:

3.60 RETAIL/CEX
release: 0x03600011 build: CEX security-repository-path: release_branches/release_03.600 security-revision: 6782 sys-repository-path: release_branches/release_03.600 sys-revision: 95473 sdk-internal-build-number: 109632 vsh-repository-path: release_branches/release_03.600 vsh-revision: 142469 vsh-build-number: 75388

3.60 DEBUG/DEX
release: 0x03600011 build: DEX security-repository-path: release_branches/release_03.600 security-revision: 6782 sys-repository-path: release_branches/release_03.600 sys-revision: 95473 sdk-internal-build-number: 109632 vsh-repository-path: release_branches/release_03.600 vsh-revision: 142469 vsh-build-number: 75388

3.57 RETAIL/CEX
release: build: CEX security-repository-path: security-revision: sys-repository-path: sys-revision: sdk-internal-build-number: vsh-repository-path: vsh-revision: vsh-build-number:

3.55 RETAIL/CEX
release: 0x03550011 build: CEX security-repository-path: release_branches/release_03.550 security-revision: 6755 sys-repository-path: release_branches/release_03.550 sys-revision: 94794 sdk-internal-build-number: 109189 vsh-repository-path: release_branches/release_03.550 vsh-revision: 142203 vsh-build-number: 750945

3.52 RETAIL/CEX
release: 0x03520011 build: CEX security-repository-path: release_branches/release_03.520 security-revision: 6739 sys-repository-path: release_branches/release_03.520 sys-revision: 94376 sdk-internal-build-number: 108837 vsh-repository-path: release_branches/release_03.520 vsh-revision: 141973 vsh-build-number: 748630

3.36 RETAIL/CEX
release: 0x03360011 build: CEX security-repository-path: release_branches/release_03.360 security-revision: 6667 sys-repository-path: release_branches/release_03.360 sys-revision: 92996 sdk-internal-build-number: 107658 vsh-repository-path: release_branches/release_03.360 vsh-revision: 140607 vsh-build-number: 73834

3.18 RETAIL/CEX
release: 0x03180011 build: CEX security-repository-path: release_branches/release_03.180 security-revision: 6593 sys-repository-path: release_branches/release_03.180 sys-revision: 90996 sdk-internal-build-number: 106092 vsh-repository-path: release_branches/release_03.180 vsh-revision: 136855 vsh-build-number: 71449

3.15 RETAIL/CEX
release: 0x03150021 build: CEX security-repository-path: release_branches/release_03.150 security-revision: 6504 sys-repository-path: release_branches/release_03.150 sys-revision: 89732 sdk-internal-build-number: 104838 vsh-repository-path: release_branches/release_03.150 vsh-revision: 133376 vsh-build-number: 69811

3.01 RETAIL/CEX
release: 0x03010031 build: CEX security-repository-path: release_branches/release_03.010 security-revision: 6412 sys-repository-path: release_branches/release_03.010 sys-revision: 87561 sdk-internal-build-number: 102567 vsh-repository-path: release_branches/release_03.010 vsh-revision: 127742 vsh-build-number: 66858

1.52 RETAIL/CEX
release: 0x01520011 build: CEX security-repository-path: release_branches/release_01.520 security-revision: 5135 sys-repository-path: release_branches/release_01.520 sys-revision: 62515 sdk-internal-build-number: 77206 vsh-repository-path: release_branches/release_01.520 vsh-revision: 84399 vsh-build-number: 405413 Product Code: CEX_E12 Settings format Version:001.500.61