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This file is generated on app package generation based on the passcode provided. It is then included in every savedata and trophy created by the application.
This file is generated on app package generation based on the passcode provided. It is then included in every savegame created by the app.
It is used to prevent apps from mounting savedata of other apps, as you need to know at least the fingerprint to do it.


It is used to prevent applications from mounting savedata of other applications, as you need to know at least the fingerprint to do it.
== Passcode ==


See also [https://wiki.henkaku.xyz/vita/Keystone PS Vita Keystone].
The passcode is a 32 character string used on package generation to create the keystone file.
 
= PS4 =
 
== Location ==
 
The keystone file is located in the sce_sys folder of every applications/patches/additional contents/savedata/trophies. It is PFS encrypted.
 
<save data directory>:/sce_sys/keystone


== Structure ==
== Structure ==


Size is always 96 bytes.
Size is always 96 (0x60) bytes for both PS4 and PSVita.


{| class="wikitable"
{| class="wikitable"
! Offset !! Size !! Description !! Notes
! Offset !! Size !! Description !! Example
|-
|-
| 0x0 || 0x8 || Magic || "keystone"
| 0x0 || 0x20 || MAGIC ("keystone") and some constant bytes || 6b 65 79 73 74 6f 6e 65 02 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
|-
|-
| 0x8 || 0x2 || Type || always 2
| 0x20 || 0x20 || HMAC-SHA256 (32 bytes) of the bytes of the passcode using keystone_passcode_secret as key ||
|-
|-
| 0xA || 0x2 || Version || always 1
| 0x40 || 0x20 || HMAC-SHA256 (32 bytes) of the previous two sections using keystone_ks_secret as key ||
|-
| 0xC || 0x14 || Padding || always zeroed
|-
| 0x20 || 0x20 || Passcode Digest || HMAC-SHA256 digest made with keystone_passcode_secret as key
|-
| 0x40 || 0x20 || Keystone Digest || HMAC-SHA256 digest made with keystone_ks_secret as key
|}
|}


== Usage ==
== Sample keystone file generation ==
 
'''CSharp'''
=== Generation ===
 
SCE provides in official PS4 SDK a tool called pc2ks that converts a passcode to a keystone.
 
Below is a simple reimplementation of PS4 pc2ks in '''python3''' by SocraticBliss.
<source lang="python3">
from binascii import unhexlify as uhx
import hashlib
import hmac
import sys
 
keystone_passcode_secret = uhx('C74405F67424BA342BC1276251BBC2F555F16025B6A1B6714780DBAEC852FA2F')
keystone_ks_secret = uhx('783D6F3AE91C0E0712FCAAB7950BDE06855CF7A22DCDBDE127E9BFCBAD0FF0FE')
 
keystone = '6B657973746F6E65020001000000000000000000000000000000000000000000'
 
def main(argc, argv):
    passcode = '00000000000000000000000000000000'
 
    if argc == 2:
        if len(argv[1]) == 32:
            passcode = argv[1]
        else:
            print('\nERROR: Passcode Must Be 32 Digits!')
            sys.exit(1)
 
    print('\npasscode = %s' % passcode)
    fingerprint = hmac.new(keystone_passcode_secret, passcode.encode(encoding = 'UTF-8'), hashlib.sha256).hexdigest().upper()
    print('fingerprint = %s' % fingerprint)
    sha256hmac  = hmac.new(keystone_ks_secret, uhx(keystone + fingerprint), hashlib.sha256).hexdigest().upper()
    print('sha256hmac  = %s' % sha256hmac)
 
    print('\nkeystone\n%s\n%s\n%s' % (keystone, fingerprint, sha256hmac))
 
if __name__=='__main__':
    sys.exit(main(len(sys.argv), sys.argv))
</source>
 
Below is a simple reimplementation of PS4 pc2ks in '''CSharp'''.
<source lang="csharp">
<source lang="csharp">
public static byte [] GenerateKeystoneFile (string passcode)
public static byte [] GenerateKeystoneFile (string passcode)
Line 102: Line 49:
     // 6. Concat the constant bytes from point 1, the fingerprint from point 3 and the hmac from point 5
     // 6. Concat the constant bytes from point 1, the fingerprint from point 3 and the hmac from point 5
     keystone = keystone.Concat(sha256hmac).ToArray();
     keystone = keystone.Concat(sha256hmac).ToArray();


     return keystone;
     return keystone;
}
}
</source>
</source>


=== Verification ===
== Sample keystone file ==
 
The first step is to check the Digest of the keystone file (using VerifyKeystone). The process is to use the <code>keystone_ks_secret</code> to check the <code>keystone Digest</code> at position 0x40 in the file.
 
If it is correct, it proceeds to check the passcode Digest, ?which is not present on retail units?. Use <code>keystone_passcode_secret</code> to calculate the digest of the <code>passcode</code> stored at offset 0x20.


= Sample keystone file =
Sample keystone file created when provided a passcode consisting of all zeros "00000000000000000000000000000000":
 
Below is a sample keystone file created when provided a passcode consisting of all zeros "00000000000000000000000000000000":
<pre>
<pre>
The first 32 are constant:
The first 32 are constant:
00000000  6b 65 79 73 74 6f 6e 65 02 00 01 00 00 00 00 00  |keystone........|
00000000  6b 65 79 73 74 6f 6e 78 02 00 01 00 00 00 00 00  |keystone........|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
Fingerprint of the passcode:
Fingerprint of the passcode:
00000020  29 4a 5e d0 6d b1 70 61  8f 2e ed 8c 42 4b 9d 82  |)J^.m.pa....BK..|
00000020  29 4a 5e 87 6d b1 70 61  8f 2e ed 8c 42 4b 9d 82  |)J^.m.pa....BK..|
00000030  88 79 c0 80 cc 66 fb c4  86 4f 69 e9 74 de b8 56  |.y...f...Oi.t..V|
00000030  88 79 c0 80 cc 66 fb c4  86 4f 69 e9 74 de b8 56  |.y...f...Oi.t..V|
SHA256Hmac of the first 64 bytes of the file:
SHA256Hmac of the first 64 bytes of the file:
00000040  fa 0d 0c 2e bd 6a 00 80  63 71 3d e8 81 0d 7e 10  |.....j..cq=...~.|
00000040  fa 0d 0c 2e bd 6a 00 80  63 71 3d e8 81 0d 7e 10  |.....j..cq=...~.|
00000050  b7 32 14 3b 91 cd 2e 4f  ea 2d 20 53 10 6e b7 5d  |.2.;...O.- S.n.]|
00000050  b7 50 98 3b 91 cd 2e 4f  ea 2d 20 53 10 6e b7 5d  |.2.;...O.- S.n.]|
</pre>
</pre>
{{File Formats}}
<noinclude>[[Category:Main]]</noinclude>
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