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Platform Security

Table of Contents

  1. IBM TPM 2.0 Simulator
  2. File Measurements using PCR Registers
  3. Endorsement Keys
  4. Attestation Keys

IBM TPM 2.0 Simulator

We run the IBM TPM 2.0 simulator in a docker container and access it with the tpm2-tools via the tpm2-tss software stack .

We clone the TPM docker-compose environment which automatically installs the strongx509/tpm docker image and brings the tpm-server container up:

$ git clone https://github.com/strongX509/docker.git
$ cd docker/tpm
$ docker-compose up
Creating tpm-server ... done
Attaching to tpm-server

In an additional console window we open a bash shell to start the IBM TPM 2.0 simulator in the tpm-server container

$ docker exec -ti tpm-server /bin/bash
# /usr/bin/tpm_server &
LIBRARY_COMPATIBILITY_CHECK is ON
Manufacturing NV state...
Size of OBJECT = 2600
Size of components in TPMT_SENSITIVE = 1096
    TPMI_ALG_PUBLIC                 2
    TPM2B_AUTH                      66
    TPM2B_DIGEST                    66
    TPMU_SENSITIVE_COMPOSITE        962
Starting ACT thread...
TPM command server listening on port 2321
Platform server listening on port 2322

After tpm_server has started in the background, its internal state must be initialized first

# tpm2_startup -c 
Command IPv4 client accepted
Platform IPv4 client accepted
Platform server listening on port 2322
TPM command server listening on port 2321

Since the tpm_server daemon generates the four output lines above every time a TPM command is received it might better to suppress the debug output when starting the daemon

# kill %1
# /usr/bin/tpm_server > /dev/null &
# tpm2_startup -c

Now the TPM 2.0 simulator is ready to use.

File Measurements using PCR Registers

First we list the contents of the sha256 PCR bank

# tpm2_pcrread sha256
sha256:
  0 : 0x0000000000000000000000000000000000000000000000000000000000000000
  1 : 0x0000000000000000000000000000000000000000000000000000000000000000
  2 : 0x0000000000000000000000000000000000000000000000000000000000000000
  3 : 0x0000000000000000000000000000000000000000000000000000000000000000
  4 : 0x0000000000000000000000000000000000000000000000000000000000000000
  5 : 0x0000000000000000000000000000000000000000000000000000000000000000
  6 : 0x0000000000000000000000000000000000000000000000000000000000000000
  7 : 0x0000000000000000000000000000000000000000000000000000000000000000
  8 : 0x0000000000000000000000000000000000000000000000000000000000000000
  9 : 0x0000000000000000000000000000000000000000000000000000000000000000
  10: 0x0000000000000000000000000000000000000000000000000000000000000000
  11: 0x0000000000000000000000000000000000000000000000000000000000000000
  12: 0x0000000000000000000000000000000000000000000000000000000000000000
  13: 0x0000000000000000000000000000000000000000000000000000000000000000
  14: 0x0000000000000000000000000000000000000000000000000000000000000000
  15: 0x0000000000000000000000000000000000000000000000000000000000000000
  16: 0x0000000000000000000000000000000000000000000000000000000000000000
  17: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  18: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  19: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  20: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  21: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  22: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  23: 0x0000000000000000000000000000000000000000000000000000000000000000

For legacy applications also a sha1 PCR bank is available

tpm2_pcrread sha1
sha1:
  0 : 0x0000000000000000000000000000000000000000
  1 : 0x0000000000000000000000000000000000000000
  2 : 0x0000000000000000000000000000000000000000
  3 : 0x0000000000000000000000000000000000000000
  4 : 0x0000000000000000000000000000000000000000
  5 : 0x0000000000000000000000000000000000000000
  6 : 0x0000000000000000000000000000000000000000
  7 : 0x0000000000000000000000000000000000000000
  8 : 0x0000000000000000000000000000000000000000
  9 : 0x0000000000000000000000000000000000000000
  10: 0x0000000000000000000000000000000000000000
  11: 0x0000000000000000000000000000000000000000
  12: 0x0000000000000000000000000000000000000000
  13: 0x0000000000000000000000000000000000000000
  14: 0x0000000000000000000000000000000000000000
  15: 0x0000000000000000000000000000000000000000
  16: 0x0000000000000000000000000000000000000000
  17: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  18: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  19: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  20: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  21: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  22: 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  23: 0x0000000000000000000000000000000000000000

The PCR banks implemented by the TPM simulator can be listed with

# tpm2_getcap pcrs
selected-pcrs:
  - sha1: [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 ]
  - sha256: [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 ]
  - sha384: [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 ]
  - sha512: [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 ]

Currently available TPM devices usually support sha1 and sha256, only.

Now we determine the sha1 and sha256 hashes of the bin/bashfile

# sha1sum /bin/bash
6b6843dae13e009a3267eed8f472bebe47e39e31  /bin/bash
# sha256sum /bin/bash
2c336c63e26881d2f02f34379024e7c314bce572c08cbaa319bacbbec29f93ed  /bin/bash

and extend these values into PCR 10 of both the sha256 and sha1 PCR banks

tpm2_pcrextend 10:sha256=2c336c63e26881d2f02f34379024e7c314bce572c08cbaa319bacbbec29f93ed,sha1=6b6843dae13e009a3267eed8f472bebe47e39e31

We are interested in the extended state of the PCR 10 registers only

# tpm2_pcrread sha1:10+sha256:10
  sha1:
    10: 0x24FC4C679DFEF3C24E0BA32F371B380991A1A6BA
  sha256:
    10: 0x1471960C96CB1946ACCCCDE5DB98BD175298F90E43F92F47635C7D0594A59D8D

Now we compute the sha256 hash of the /bin/cp/ file

# sha256sum /bin/cp
5cbd6e8d5aaa714a0910f5ee7710004cbf0a22c940eda1abec6f0194f430b94c  /bin/cp

and extend it into registers 10 and 16 of the sha256 PCR bank

tpm2_pcrextend 10:sha256=5cbd6e8d5aaa714a0910f5ee7710004cbf0a22c940eda1abec6f0194f430b94c 16:sha256=5cbd6e8d5aaa714a0910f5ee7710004cbf0a22c940eda1abec6f0194f430b94c

The following registers have now been extended

# tpm2_pcrread sha1:10+sha256:10,16
  sha1:
    10: 0x24FC4C679DFEF3C24E0BA32F371B380991A1A6BA
  sha256:
    10: 0x13DBDF26B9BAB4A8FDF2FCFF30C560D7BFA5334B762318BCD859EB743985C592
    16: 0xD56AF09F9243A7F156C525AFA276F647BEF55F69C67D6F5F8A6F34B9626E2E9B

We try to reset register 10 in all PCR banks

# tpm2_pcrreset 10
WARNING:esys:src/tss2-esys/api/Esys_PCR_Reset.c:287:Esys_PCR_Reset_Finish() Received TPM Error 
ERROR:esys:src/tss2-esys/api/Esys_PCR_Reset.c:98:Esys_PCR_Reset() Esys Finish ErrorCode (0x00000907) 
ERROR: Esys_PCR_Reset(0x907) - tpm:warn(2.0): bad locality
ERROR: Could not reset PCR index: 10
ERROR: Unable to run tpm2_pcrreset

Fortunately this is not possible. Otherwise malicious malware could reset the PCR registers and extend them with fake measurements. On a PC motherboard only a cold reboot resets the PCR values.

An exception is PCR 16 that is intended for test purposes and thus can be reset

# tpm2_pcrreset 16
# tpm2_pcrread sha1:10+sha256:10,16
  sha1:
    10: 0x24FC4C679DFEF3C24E0BA32F371B380991A1A6BA
  sha256:
    10: 0x13DBDF26B9BAB4A8FDF2FCFF30C560D7BFA5334B762318BCD859EB743985C592
    16: 0x0000000000000000000000000000000000000000000000000000000000000000

We see that PCR 16 has been reset to all zeroes.

Endorsement Keys

Each TPM has unique non-erasable Endorsement Seed. From this seed an Endorsement Key EK of any chosen key type can be derived in a deterministic way.

RSA Endorsement Key

First we derive an RSA EK and store it in non-volatile RAM under the handle 0x81010001

# tpm2_createek -G rsa3072 -c 0x81010001
# tpm2_getcap handles-persistent
- 0x81010001

With the help of its tpmplugin the strongSwan pki tool can read the unique keyid of a private key stored in a TPM based on its handle

# pki --print --type priv --keyid 0x81010001
TPM 2.0 via TSS2 v2 available
encryption algorithm is AES-CFB with 256 bits
  privkey:   RSA 3072 bits
  keyid:     4f:8b:b8:02:3d:e0:cd:83:5e:47:b5:ff:68:28:20:d7:72:18:34:e6
  subjkey:   a9:22:9c:54:f0:56:da:57:d5:7d:70:07:7d:d9:a3:c7:af:4c:6c:f7

Since no signature algorithm is defined we notice that an EK is a decryption key and thus cannot be used for signatures.

In order for pki to connect correctly to the TPM simulator the mssim driver must be specified explicitly in /etc/strongswan.conf

# cat /etc/strongswan.conf
pki {
   plugins {
      tpm {
         tcti {
            name = mssim
         }
      }
   }
}

Public Key Extraction

The pki tool can extract the public key in standard PKCS#1 format. During the extraction we increase the debug level to 3 thus showing the encoding of the public key.

# pki --pub --type priv --keyid 0x81010001 --outform pem --debug 3 > ek_rsa.pem

The debug output first displays the device manufacturer and then lists some capabilities of the TPM

TPM 2.0 - manufacturer: IBM  (SW   TPM) rev: 01.62 2020 FIPS 140-2
TPM 2.0 - algorithms: RSA SHA1 HMAC AES MGF1 KEYEDHASH XOR SHA256 SHA384 SHA512 RSASSA RSAES RSAPSS OAEP ECDSA ECDH ECDAA ECSCHNORR KDF1_SP800_56A KDF2 KDF1_SP800_108 ECC SYMCIPHER CAMELLIA CMAC CTR OFB CBC CFB ECB
TPM 2.0 - ECC curves: NIST_P256 NIST_P384 BN_P256
TPM 2.0 - PCR banks: SHA1 SHA256 SHA384 SHA512
TPM 2.0 via TSS2 v2 available

Then the PKCS#1 encoding of the public key follows:

L0 - subjectPublicKeyInfo:
L1 - algorithm:
L2 - algorithmIdentifier:
L3 - algorithm:
  'rsaEncryption'
L3 - parameters:
=> 2 bytes @ 0x55dffd163d31
   0: 05 00                                            ..
L1 - subjectPublicKey:
=> 399 bytes @ 0x55dffd163d37
   0: 00 30 82 01 8A 02 82 01 81 00 99 7E 46 95 C0 13  .0.........~F...
  16: AE 0F A0 74 02 17 BB FD 5B A5 EC 5F D1 A3 98 FA  ...t....[.._....
  32: F9 D7 97 6B 67 BA 58 87 01 CE E3 9A 89 9A AF 02  ...kg.X.........
  48: B7 46 E0 53 4B 91 09 59 2C 08 47 90 26 C0 8A 8B  .F.SK..Y,.G.&...
  64: F7 9A DE 75 3F D6 73 50 5F 0A F2 0E D4 1F 7F 5C  ...u?.sP_......\
  80: D5 88 0C BE 8E 4B F6 B0 AC A6 1D 9F A5 62 05 1F  .....K.......b..
  96: 28 00 AD 12 84 32 FC BA A5 7D 93 63 F4 3E 0F 69  (....2...}.c.>.i
 112: D0 86 BD 84 84 DD 5C D3 A5 91 BE 10 85 0D 9A 5E  ......\........^
 128: E1 F8 57 9C 6E 74 55 61 EF 90 86 4A EC 83 B3 55  ..W.ntUa...J...U
 144: 4E 89 8C E7 E4 7D 7E 16 AA 73 39 B4 04 0A D7 82  N....}~..s9.....
 160: 38 0B A7 AF 78 F3 6D 86 A7 09 F1 B6 55 D1 C3 08  8...x.m.....U...
 176: 5A AF ED 2D 19 90 EB DC 68 E2 5C 34 E0 43 1B B2  Z..-....h.\4.C..
 192: 7C 8B 10 38 84 E3 E7 C1 21 FF 6A B9 29 7B F1 CB  |..8....!.j.){..
 208: 1A 67 65 73 89 E8 50 1C 69 E1 48 6C 36 F4 73 4B  .ges..P.i.Hl6.sK
 224: B2 09 30 50 F6 57 EE 92 EC 52 16 CF 2B 00 52 01  ..0P.W...R..+.R.
 240: FA B9 78 15 B6 3F C4 2C 8D B6 B1 79 1F AB 2A 03  ..x..?.,...y..*.
 256: 1F 5F 51 CA A8 FC C6 9D 72 4E 64 BC 1A 17 55 77  ._Q.....rNd...Uw
 272: 12 CB 3D 77 17 9D 26 5E 52 B1 94 FB 52 72 5D AE  ..=w..&^R...Rr].
 288: 97 E0 57 4F 4F 27 41 26 01 76 1F 65 04 06 A8 09  ..WOO'A&.v.e....
 304: 33 35 D1 5E 7E AF DC C2 13 4D 80 DF D2 0E DA 18  35.^~....M......
 320: 6C EC A7 DF C1 32 A4 3D 8F A7 D6 7D 45 DB 6F 97  l....2.=...}E.o.
 336: FE 25 30 C8 30 B2 98 2E DE 33 C7 B2 15 DE A8 1F  .%0.0....3......
 352: B1 60 8B 93 83 07 E1 FA 1F 62 91 00 38 56 CE 10  .`.......b..8V..
 368: 79 50 C4 09 56 64 93 76 F5 2A E5 99 DA 35 95 79  yP..Vd.v.*...5.y
 384: 60 77 A4 39 24 81 97 17 3B C3 02 03 01 00 01     `w.9$...;......
-- > --
L0 - RSAPublicKey:
=> 398 bytes @ 0x55dffd163d38
   0: 30 82 01 8A 02 82 01 81 00 99 7E 46 95 C0 13 AE  0.........~F....
  16: 0F A0 74 02 17 BB FD 5B A5 EC 5F D1 A3 98 FA F9  ..t....[.._.....
  32: D7 97 6B 67 BA 58 87 01 CE E3 9A 89 9A AF 02 B7  ..kg.X..........
  48: 46 E0 53 4B 91 09 59 2C 08 47 90 26 C0 8A 8B F7  F.SK..Y,.G.&....
  64: 9A DE 75 3F D6 73 50 5F 0A F2 0E D4 1F 7F 5C D5  ..u?.sP_......\.
  80: 88 0C BE 8E 4B F6 B0 AC A6 1D 9F A5 62 05 1F 28  ....K.......b..(
  96: 00 AD 12 84 32 FC BA A5 7D 93 63 F4 3E 0F 69 D0  ....2...}.c.>.i.
 112: 86 BD 84 84 DD 5C D3 A5 91 BE 10 85 0D 9A 5E E1  .....\........^.
 128: F8 57 9C 6E 74 55 61 EF 90 86 4A EC 83 B3 55 4E  .W.ntUa...J...UN
 144: 89 8C E7 E4 7D 7E 16 AA 73 39 B4 04 0A D7 82 38  ....}~..s9.....8
 160: 0B A7 AF 78 F3 6D 86 A7 09 F1 B6 55 D1 C3 08 5A  ...x.m.....U...Z
 176: AF ED 2D 19 90 EB DC 68 E2 5C 34 E0 43 1B B2 7C  ..-....h.\4.C..|
 192: 8B 10 38 84 E3 E7 C1 21 FF 6A B9 29 7B F1 CB 1A  ..8....!.j.){...
 208: 67 65 73 89 E8 50 1C 69 E1 48 6C 36 F4 73 4B B2  ges..P.i.Hl6.sK.
 224: 09 30 50 F6 57 EE 92 EC 52 16 CF 2B 00 52 01 FA  .0P.W...R..+.R..
 240: B9 78 15 B6 3F C4 2C 8D B6 B1 79 1F AB 2A 03 1F  .x..?.,...y..*..
 256: 5F 51 CA A8 FC C6 9D 72 4E 64 BC 1A 17 55 77 12  _Q.....rNd...Uw.
 272: CB 3D 77 17 9D 26 5E 52 B1 94 FB 52 72 5D AE 97  .=w..&^R...Rr]..
 288: E0 57 4F 4F 27 41 26 01 76 1F 65 04 06 A8 09 33  .WOO'A&.v.e....3
 304: 35 D1 5E 7E AF DC C2 13 4D 80 DF D2 0E DA 18 6C  5.^~....M......l
 320: EC A7 DF C1 32 A4 3D 8F A7 D6 7D 45 DB 6F 97 FE  ....2.=...}E.o..
 336: 25 30 C8 30 B2 98 2E DE 33 C7 B2 15 DE A8 1F B1  %0.0....3.......
 352: 60 8B 93 83 07 E1 FA 1F 62 91 00 38 56 CE 10 79  `.......b..8V..y
 368: 50 C4 09 56 64 93 76 F5 2A E5 99 DA 35 95 79 60  P..Vd.v.*...5.y`
 384: 77 A4 39 24 81 97 17 3B C3 02 03 01 00 01        w.9$...;......
L1 - modulus:
=> 385 bytes @ 0x55dffd163d40
   0: 00 99 7E 46 95 C0 13 AE 0F A0 74 02 17 BB FD 5B  ..~F......t....[
  16: A5 EC 5F D1 A3 98 FA F9 D7 97 6B 67 BA 58 87 01  .._.......kg.X..
  32: CE E3 9A 89 9A AF 02 B7 46 E0 53 4B 91 09 59 2C  ........F.SK..Y,
  48: 08 47 90 26 C0 8A 8B F7 9A DE 75 3F D6 73 50 5F  .G.&......u?.sP_
  64: 0A F2 0E D4 1F 7F 5C D5 88 0C BE 8E 4B F6 B0 AC  ......\.....K...
  80: A6 1D 9F A5 62 05 1F 28 00 AD 12 84 32 FC BA A5  ....b..(....2...
  96: 7D 93 63 F4 3E 0F 69 D0 86 BD 84 84 DD 5C D3 A5  }.c.>.i......\..
 112: 91 BE 10 85 0D 9A 5E E1 F8 57 9C 6E 74 55 61 EF  ......^..W.ntUa.
 128: 90 86 4A EC 83 B3 55 4E 89 8C E7 E4 7D 7E 16 AA  ..J...UN....}~..
 144: 73 39 B4 04 0A D7 82 38 0B A7 AF 78 F3 6D 86 A7  s9.....8...x.m..
 160: 09 F1 B6 55 D1 C3 08 5A AF ED 2D 19 90 EB DC 68  ...U...Z..-....h
 176: E2 5C 34 E0 43 1B B2 7C 8B 10 38 84 E3 E7 C1 21  .\4.C..|..8....!
 192: FF 6A B9 29 7B F1 CB 1A 67 65 73 89 E8 50 1C 69  .j.){...ges..P.i
 208: E1 48 6C 36 F4 73 4B B2 09 30 50 F6 57 EE 92 EC  .Hl6.sK..0P.W...
 224: 52 16 CF 2B 00 52 01 FA B9 78 15 B6 3F C4 2C 8D  R..+.R...x..?.,.
 240: B6 B1 79 1F AB 2A 03 1F 5F 51 CA A8 FC C6 9D 72  ..y..*.._Q.....r
 256: 4E 64 BC 1A 17 55 77 12 CB 3D 77 17 9D 26 5E 52  Nd...Uw..=w..&^R
 272: B1 94 FB 52 72 5D AE 97 E0 57 4F 4F 27 41 26 01  ...Rr]...WOO'A&.
 288: 76 1F 65 04 06 A8 09 33 35 D1 5E 7E AF DC C2 13  v.e....35.^~....
 304: 4D 80 DF D2 0E DA 18 6C EC A7 DF C1 32 A4 3D 8F  M......l....2.=.
 320: A7 D6 7D 45 DB 6F 97 FE 25 30 C8 30 B2 98 2E DE  ..}E.o..%0.0....
 336: 33 C7 B2 15 DE A8 1F B1 60 8B 93 83 07 E1 FA 1F  3.......`.......
 352: 62 91 00 38 56 CE 10 79 50 C4 09 56 64 93 76 F5  b..8V..yP..Vd.v.
 368: 2A E5 99 DA 35 95 79 60 77 A4 39 24 81 97 17 3B  *...5.y`w.9$...;
 384: C3                                               .
L1 - publicExponent:
=> 3 bytes @ 0x55dffd163ec3
   0: 01 00 01 
   -- < --

Similar information can be obtained with openssl

# openssl rsa -in ek_rsa.pem -pubin -noout -text
Public-Key: (3072 bit)
Modulus:
    00:99:7e:46:95:c0:13:ae:0f:a0:74:02:17:bb:fd:
    5b:a5:ec:5f:d1:a3:98:fa:f9:d7:97:6b:67:ba:58:
    87:01:ce:e3:9a:89:9a:af:02:b7:46:e0:53:4b:91:
    09:59:2c:08:47:90:26:c0:8a:8b:f7:9a:de:75:3f:
    d6:73:50:5f:0a:f2:0e:d4:1f:7f:5c:d5:88:0c:be:
    8e:4b:f6:b0:ac:a6:1d:9f:a5:62:05:1f:28:00:ad:
    12:84:32:fc:ba:a5:7d:93:63:f4:3e:0f:69:d0:86:
    bd:84:84:dd:5c:d3:a5:91:be:10:85:0d:9a:5e:e1:
    f8:57:9c:6e:74:55:61:ef:90:86:4a:ec:83:b3:55:
    4e:89:8c:e7:e4:7d:7e:16:aa:73:39:b4:04:0a:d7:
    82:38:0b:a7:af:78:f3:6d:86:a7:09:f1:b6:55:d1:
    c3:08:5a:af:ed:2d:19:90:eb:dc:68:e2:5c:34:e0:
    43:1b:b2:7c:8b:10:38:84:e3:e7:c1:21:ff:6a:b9:
    29:7b:f1:cb:1a:67:65:73:89:e8:50:1c:69:e1:48:
    6c:36:f4:73:4b:b2:09:30:50:f6:57:ee:92:ec:52:
    16:cf:2b:00:52:01:fa:b9:78:15:b6:3f:c4:2c:8d:
    b6:b1:79:1f:ab:2a:03:1f:5f:51:ca:a8:fc:c6:9d:
    72:4e:64:bc:1a:17:55:77:12:cb:3d:77:17:9d:26:
    5e:52:b1:94:fb:52:72:5d:ae:97:e0:57:4f:4f:27:
    41:26:01:76:1f:65:04:06:a8:09:33:35:d1:5e:7e:
    af:dc:c2:13:4d:80:df:d2:0e:da:18:6c:ec:a7:df:
    c1:32:a4:3d:8f:a7:d6:7d:45:db:6f:97:fe:25:30:
    c8:30:b2:98:2e:de:33:c7:b2:15:de:a8:1f:b1:60:
    8b:93:83:07:e1:fa:1f:62:91:00:38:56:ce:10:79:
    50:c4:09:56:64:93:76:f5:2a:e5:99:da:35:95:79:
    60:77:a4:39:24:81:97:17:3b:c3
Exponent: 65537 (0x10001)

ECC Endorsement Key

As an alternative we can derive an ECC EK based on Elliptic Curve Cryptography from the same secret Endorsement Seed and store it persistenly under the handle 0x81010002

# tpm2_createek -G ecc384 -c 0x81010002
# tpm2_getcap handles-persistent
- 0x81010001
- 0x81010002

The pki tool identifies the second EK as a 256 bit ECDSA decryption key

# pki --print --type priv --keyid 0x81010002
TPM 2.0 via TSS2 v2 available
encryption algorithm is AES-CFB with 256 bits
  privkey:   ECDSA 384 bits
  keyid:     ac:bf:5f:9e:7b:bc:f2:82:dc:cf:67:db:62:01:cb:5d:73:93:66:f6
  subjkey:   d1:54:63:9e:3c:aa:0c:a9:03:a0:fb:fb:6c:0f:ef:16:bd:1f:89:e5

Key Removal from Persistent Memory

If we run out of non-volatile memory we can delete an Endorsement Key at any time

# tpm2_evictcontrol -c 0x81010001
persistent-handle: 0x81010001
action: evicted
# tpm2_getcap handles-persistent
- 0x81010002

and can derive it again when the need occurs

# tpm2_createek -G rsa3072 -c 0x81010001
# pki --print --type priv --keyid 0x81010001
TPM 2.0 via TSS2 v2 available
encryption algorithm is AES-CFB with 256 bits
  privkey:   RSA 3072 bits
  keyid:     4f:8b:b8:02:3d:e0:cd:83:5e:47:b5:ff:68:28:20:d7:72:18:34:e6
  subjkey:   a9:22:9c:54:f0:56:da:57:d5:7d:70:07:7d:d9:a3:c7:af:4c:6c:f7

As can be easily verified the same EK as before results.

Attestation Keys

Under the Endorsement Hierarchy we can create as many random signature keys as we need for our applications. Microsoft calls this the Virtual Smartcard functionality of a TPM.

Built-In True Random Generator

In order to generate RSA or ECC keys the TPM needs a built-in True Random Generator.

# tpm2_getrandom --hex 10
54be6d8a4c041177ccc7

Up to 64 random bytes can be extracted in single call by tpm2_getrandom

RSA Attestation Key

We generate a random RSA Attestation Key AK protected by the RSA Endorsement Key EK with handle 0x81010001and store it in the context file ak_rsa.ctx. The use of the Attestation Key is protected by the password 123456.

# tpm2_createak -C 0x81010001 -G rsa3072 -g sha256 -s rsassa -p 123456 -c ak_rsa.ctx -u ak_rsa.pub -n ak_rsa.name
loaded-key:
  name: 000c3e9c99092f2eb88e158eaaaa454fa45c3e33bb8bed3a42f8fd9849bbe95ed755cbb70513c50309b6d0c281e4b4d51f84
  qualified name: 000c4cb4c6b23ccc1c2893564ea96bc6fc6c33c3fceef821b44a04c3ca66300083ca69c1aba0248b8053aede35385909ef40

We then persist the key under the handle 0x81010003

# tpm2_evictcontrol -C o -c ak_rsa.ctx 0x81010003
persistent-handle: 0x81010003
action: persisted

The pki command shows that a RSA signature key has been generated

# pki --print --type priv --keyid 0x81010003
TPM 2.0 via TSS2 v2 available
signature algorithm is RSASSA with SHA256 hash
  privkey:   RSA 3072 bits
  keyid:     65:3b:d0:d1:6c:a6:d3:72:0c:c6:d2:2e:ac:e8:ec:ad:97:0c:8e:e5
  subjkey:   03:a3:d4:16:34:02:02:c8:25:ae:41:89:32:e8:90:72:9b:31:be:aa

If a client wants to authenticate itself using this RSA key then it needs an X.509 certificate issued and signed by a trusted Certification Authority CA. Therefore a standard PKCS#10 Certificate Request is generated by the pkitool signed by the private AK stored in the TPM.

# pki --req --keyid 0x81010003 --outform pem --dn "C=CH, O=Cyber, OU=user@strongswan.org" --san user@strongswan.org > ak_rsa_Req.pem
TPM 2.0 via TSS2 v2 available
signature algorithm is RSASSA with SHA256 hash
Smartcard PIN:
123456

For the TPM signature the password is requested.

We visualize the PKCS#10 Certificate Request using openssl before sending the request to the Certification Authority

# openssl req -in ak_rsa_Req.pem -noout -text
Certificate Request:
    Data:
        Version: 1 (0x0)
        Subject: C = CH, O = Cyber, OU = user@strongswan.org
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (3072 bit)
                Modulus:
                    00:83:b6:63:fa:e6:df:91:44:63:ee:96:4f:4a:83:
                    03:09:5f:0c:d7:55:40:eb:fb:17:bf:65:fc:33:8f:
                    d2:66:34:f1:1e:b4:d4:15:6b:4a:41:46:cd:91:a1:
                    37:c1:4a:71:1e:79:e2:e4:51:bc:46:27:ab:ce:c1:
                    0d:72:f4:3f:88:f1:fa:45:c3:43:e5:62:74:be:37:
                    87:a4:02:73:37:fa:37:ca:68:b8:fb:bd:29:1a:5a:
                    6d:04:bf:88:90:49:dd:98:e0:3b:5a:85:bf:d6:bd:
                    f1:70:83:b3:87:72:e3:d6:b9:16:66:28:8f:fd:8c:
                    36:1f:6a:94:dd:c3:69:7e:34:a9:71:93:6c:02:d3:
                    b3:7f:c5:d8:c3:ea:6e:b9:2a:17:b2:3c:66:2f:c2:
                    9b:b3:69:e5:82:96:3b:03:c7:fb:af:5c:41:a8:a3:
                    89:4a:8f:f3:eb:ca:53:5d:0b:c2:1e:55:cc:26:dd:
                    19:74:dc:24:62:a4:b9:13:ee:18:e6:98:b1:95:4e:
                    d8:5a:83:77:e5:d3:ac:52:33:86:af:b9:f5:f9:bb:
                    e7:4f:eb:fe:eb:72:02:6b:cb:de:70:cb:aa:9b:0b:
                    5a:c6:77:06:e7:7b:25:2e:08:65:4b:d2:e9:02:c4:
                    ad:d2:80:0b:e2:c5:9f:60:9e:78:60:f1:a7:e2:5c:
                    04:5d:bc:13:7e:17:cc:8a:52:20:34:32:d2:3c:1f:
                    8b:74:15:a7:31:d7:28:b6:59:00:7e:79:9c:ab:31:
                    06:93:19:20:fe:87:3b:4c:99:b6:b6:6b:1b:cf:67:
                    49:e2:7e:e0:05:84:0e:c5:c7:c3:4d:a1:a5:db:7c:
                    80:40:59:5c:ee:72:a5:cd:d7:b1:35:de:a5:12:61:
                    53:58:48:cc:c1:e0:6e:7f:e9:7a:f9:88:0c:b8:0e:
                    bd:5f:f3:37:62:82:83:bf:43:1f:83:26:e5:b9:46:
                    ee:97:54:cf:55:03:78:fe:fb:88:db:b2:74:81:e1:
                    2d:01:90:2d:91:4b:be:60:53:bf
                Exponent: 65537 (0x10001)
        Attributes:
            Requested Extensions:
                X509v3 Subject Alternative Name: 
                    email:user@strongswan.org
    Signature Algorithm: sha256WithRSAEncryption
    Signature Value:
        42:46:47:8f:25:21:60:a0:f1:c8:d4:aa:98:b6:cf:10:ca:6a:
        96:3b:3c:b6:b3:b1:85:ef:27:ce:f6:ea:18:9d:39:2c:90:d1:
        de:35:08:55:64:87:58:86:fe:96:fc:11:6f:53:39:1c:b7:33:
        61:b4:0f:e9:4f:a4:43:e9:16:7d:b9:b5:3d:3d:8a:2a:55:27:
        af:b6:40:84:44:58:a5:7e:ea:a8:77:37:fb:51:4d:ee:8d:83:
        fa:66:35:d1:2e:a0:f7:65:c6:7f:7e:09:6e:e9:55:d8:2d:43:
        ba:14:42:43:f2:ab:3e:b2:fd:5a:e4:79:9d:2a:7c:00:4a:93:
        f7:5e:4f:c8:12:63:1f:52:91:f9:dc:86:ff:44:5a:cd:74:ba:
        d1:d5:ef:4c:01:7c:92:f7:56:ff:af:34:50:ed:53:b9:df:a3:
        0f:a5:94:2e:f7:a4:cf:13:b0:c1:05:55:71:9d:f1:40:cf:78:
        15:d5:81:d2:46:64:68:f9:e1:e9:2e:49:4b:37:19:ed:36:e4:
        e9:90:87:5f:08:e4:6f:98:03:27:2c:f2:94:c5:cc:74:e8:75:
        bf:c5:dc:03:0a:c8:2d:53:83:f4:f1:71:f3:3f:66:2e:bc:ad:
        68:3a:bd:08:f9:47:19:54:e3:f2:4f:ca:0e:79:a3:0e:1e:88:
        0d:00:72:1f:ff:f7:30:ad:a4:28:ce:2d:48:8b:2e:41:3b:fe:
        17:af:d2:3e:17:e1:73:16:cc:83:14:a9:52:4d:f8:c2:0e:e9:
        52:77:62:18:c5:1f:c0:c6:54:55:26:8b:cd:fa:6c:a9:a4:f4:
        9b:20:22:26:e5:64:3a:bf:7c:2b:7a:17:23:c7:5c:a1:03:89:
        83:f9:95:7e:fa:16:9c:68:b5:07:0c:cb:b9:c8:7f:91:56:62:
        a2:f4:f7:fd:fb:57:6a:2f:7e:9e:6d:76:51:f2:10:28:1a:7c:
        99:a7:d6:a1:96:87:04:1c:22:86:b7:d5:92:11:e5:e7:1f:e4:
        67:9f:73:b8:72:22

RSA Certification Authority

The strongSwan pki tool can be used to generate a simple Certification Authority CA. First a private CA key is generated

# pki --gen --type rsa --size 3072 --outform pem > My_RSA_CaKey.pem

and used to construct a self-signed CA certificate

# pki --self --ca --type rsa --in My_RSA_CaKey.pem --dn "C=CH, O=Cyber, CN=My RSA CA" --lifetime 3652 --outform pem > My_RSA_CaCert.pem

that looks as follows

# pki --print --type x509 --in My_RSA_CaCert.pem 
  subject:  "C=CH, O=Cyber, CN=My RSA CA"
  issuer:   "C=CH, O=Cyber, CN=My RSA CA"
  validity:  not before Oct 10 05:37:43 2022, ok
             not after  Oct 09 05:37:43 2032, ok (expires in 3651 days)
  serial:    60:75:a8:65:0e:26:b1:70
  flags:     CA CRLSign self-signed 
  subjkeyId: 03:2c:77:a4:e4:9f:0e:61:cb:cc:6d:c9:11:77:ba:ca:58:3a:a7:ef
  pubkey:    RSA 3072 bits
  keyid:     01:00:36:18:39:cb:28:69:db:06:cc:f3:7c:14:40:e1:71:15:e6:c1
  subjkey:   03:2c:77:a4:e4:9f:0e:61:cb:cc:6d:c9:11:77:ba:ca:58:3a:a7:ef

Now the user certificate can be issued based on the PKCS#10 Certificate Request

# pki --issue --cacert My_RSA_CaCert.pem --cakey My_RSA_CaKey.pem --in ak_rsa_Req.pem --type pkcs10 --flag clientAuth --lifetime 1826 > ak_rsa_Cert.der

A quick look at the X.509 certificate before it is delivered to the user

# pki --print --type x509 --in ak_rsa_Cert.der 
  subject:  "C=CH, O=Cyber, OU=user@strongswan.org"
  issuer:   "C=CH, O=Cyber, CN=My RSA CA"
  validity:  not before Oct 10 05:39:04 2022, ok
             not after  Oct 10 05:39:04 2027, ok (expires in 1825 days)
  serial:    1a:01:95:6d:7d:9d:ae:7f
  altNames:  user@strongswan.org
  flags:     clientAuth 
  authkeyId: 03:2c:77:a4:e4:9f:0e:61:cb:cc:6d:c9:11:77:ba:ca:58:3a:a7:ef
  subjkeyId: 03:a3:d4:16:34:02:02:c8:25:ae:41:89:32:e8:90:72:9b:31:be:aa
  pubkey:    RSA 3072 bits
  keyid:     65:3b:d0:d1:6c:a6:d3:72:0c:c6:d2:2e:ac:e8:ec:ad:97:0c:8e:e5
  subjkey:   03:a3:d4:16:34:02:02:c8:25:ae:41:89:32:e8:90:72:9b:31:be:aa

RSA Attestation Certificate

In order to protect the AK certificate received from the CA from accidental deletion from the system harddisk we want to store it in the Non-Volatile NV memory of the TPM. To allocate the required amount of NV memory we determine the exact size of the binary-encoded X.509 certificate

ls -l ak_rsa_Cert.der 
-rw-r--r-- 1 root root 1098 Oct 10 05:39 ak_rsa_Cert.der

and then allocate 842 bytes of NV memory under the handle 0x01800003

# tpm2_nvdefine 0x01800003 -C o -s 1098 -a 0x2000A
nv-index: 0x1800003

Now the certificate can be written into the pre-allocated memory slot

# tpm2_nvwrite 0x01800003 -C o -i ak_rsa_Cert.der

The following command shows all objects stored in NV memory

# tpm2_getcap handles-nv-index
- 0x1800003

The pki tool can display X.509 certificates stored in the TPM using the object handle

# pki --print --type x509 --keyid 0x01800003
TPM 2.0 via TSS2 v2 available
loaded certificate from TPM NV index 0x01800003
  subject:  "C=CH, O=Cyber, OU=user@strongswan.org"
  issuer:   "C=CH, O=Cyber, CN=My RSA CA"
  validity:  not before Oct 10 05:39:04 2022, ok
             not after  Oct 10 05:39:04 2027, ok (expires in 1825 days)
  serial:    1a:01:95:6d:7d:9d:ae:7f
  altNames:  user@strongswan.org
  flags:     clientAuth 
  authkeyId: 03:2c:77:a4:e4:9f:0e:61:cb:cc:6d:c9:11:77:ba:ca:58:3a:a7:ef
  subjkeyId: 03:a3:d4:16:34:02:02:c8:25:ae:41:89:32:e8:90:72:9b:31:be:aa
  pubkey:    RSA 3072 bits
  keyid:     65:3b:d0:d1:6c:a6:d3:72:0c:c6:d2:2e:ac:e8:ec:ad:97:0c:8e:e5
  subjkey:   03:a3:d4:16:34:02:02:c8:25:ae:41:89:32:e8:90:72:9b:31:be:aa

A strongSwan IKEv2 client could use the AK private key and the AK certificate stored in the TPM to authenticate itself in an IPsec connection.

Flushing the Context

From time to time it is recommended to flush the context so that the TPM doesn't run out of transient memory:

# tpm2_flushcontext -t

ECC Attestation Key

As an alternative we generate a random ECC Attestation Key AK protected by the ECC Endorsement Key EK with handle 0x81010002and persist it under the handle 0x81010004.

# tpm2_createak -C 0x81010002 -G ecc384 -g sha384 -s ecdsa -c ak_ecc.ctx -u ak_ecc.pub -n ak_ecc.name
loaded-key:
  name: 000c1713877420a369483d20fa56e760ba65494e11a08a8423eed893cd718753b3fdf810ac58b8aae22fba121f26d479942e
  qualified name: 000cb9ee290bdd27aef214c3947c74b3f81daf1b30da19ac4560dacf4fe6b0d10496ad718b83e1c2b730f438c4a8cbfdfc9b
# tpm2_evictcontrol -C o -c ak_ecc.ctx 0x81010004
persistent-handle: 0x81010004
action: persisted

The pki command shows that an ECDSA signature key has been generated

# pki --print --type priv --keyid 0x81010004
TPM 2.0 via TSS2 v2 available
signature algorithm is ECDSA with SHA384 hash
  privkey:   ECDSA 384 bits
  keyid:     fa:6a:57:e1:f7:c7:c0:2e:d3:56:d6:e5:13:4f:bb:87:ea:10:a6:66
  subjkey:   52:b0:c9:b7:62:43:da:c3:b7:60:4d:d9:d2:09:5b:55:b6:a6:46:53

In order to obtain an X.509 certificate issued and signed by a trusted Certification Authority CA we again generate a PKCS#10 Certificate Request signed by the private AK stored in the TPM.

# pki --req --keyid 0x81010004 --outform pem --dn "C=CH, O=Cyber, OU=user@strongswan.org" --san user@strongswan.org > ak_ecc_Req.pem
TPM 2.0 via TSS2 v2 available
signature algorithm is ECDSA with SHA384 hash
Smartcard PIN: 
<return>

Since no password has been configured just press the <return> key

This is how the PKCS#10 Certificate Request looks like as listed by `openssl

# openssl req -in ak_ecc_Req.pem -noout -text
Certificate Request:
    Data:
        Version: 1 (0x0)
        Subject: C = CH, O = Cyber, OU = user@strongswan.org
        Subject Public Key Info:
            Public Key Algorithm: id-ecPublicKey
                Public-Key: (384 bit)
                pub:
                    04:40:02:7a:16:58:bc:29:95:6c:81:86:0b:3f:ce:
                    8b:1c:1e:03:64:06:ea:e5:41:62:4f:85:d5:b0:8d:
                    92:f1:bf:de:59:0e:ed:8b:6e:cd:c3:b3:d0:88:66:
                    06:89:2c:c0:99:c8:89:82:16:2d:5e:e3:b5:09:27:
                    28:e2:51:c8:e3:32:6d:29:7d:44:03:f4:5d:1c:f9:
                    65:ef:8f:88:ce:7d:0a:06:11:ea:2c:93:3a:f1:8e:
                    a3:f6:5e:bc:61:48:94
                ASN1 OID: secp384r1
                NIST CURVE: P-384
        Attributes:
            Requested Extensions:
                X509v3 Subject Alternative Name: 
                    email:user@strongswan.org
    Signature Algorithm: ecdsa-with-SHA384
    Signature Value:
        30:66:02:31:00:8f:18:54:f2:c5:a8:03:73:40:84:cc:26:0d:
        d9:b7:fa:8d:49:03:4c:17:81:bf:18:97:5d:e6:8b:36:9f:e3:
        bf:72:ab:aa:8f:40:d9:42:19:34:53:1c:1c:84:80:2c:95:02:
        31:00:8e:b0:e7:0e:da:26:3d:0e:98:0c:cd:d6:42:4b:bc:c3:
        e2:4f:15:0b:a4:d6:7d:ec:1a:cd:4c:00:f4:ef:5e:3b:12:14:
        ce:65:36:bc:b9:c1:93:38:e5:28:c5:f7:7a:59

ECC Certification Authority

In order to issue ECC end entity certificates we create a Certification Authority of our own. We start be generating a private ECC key

# pki --gen --type ecdsa --size 384 --outform pem > My_ECC_CaKey.pem

and use it to construct a self-signed CA certiificate

# pki --self --ca --type ecdsa --in My_ECC_CaKey.pem --dn "C=CH, O=Cyber, CN=My ECC CA" --lifetime 3652 --outform pem > My_ECC_CaCert.pem

listed below

# pki --print --type x509 --in My_ECC_CaCert.pem 
  subject:  "C=CH, O=Cyber, CN=My ECC CA"
  issuer:   "C=CH, O=Cyber, CN=My ECC CA"
  validity:  not before Oct 10 05:52:01 2022, ok
             not after  Oct 09 05:52:01 2032, ok (expires in 3651 days)
  serial:    2d:eb:fa:2c:b4:f7:df:8c
  flags:     CA CRLSign self-signed 
  subjkeyId: 24:be:9a:27:51:71:e4:79:63:37:a1:02:e8:51:30:4b:65:19:58:59
  pubkey:    ECDSA 384 bits
  keyid:     f3:50:0c:ab:33:2f:af:87:aa:72:69:f8:95:26:2d:8c:6c:69:91:ae
  subjkey:   24:be:9a:27:51:71:e4:79:63:37:a1:02:e8:51:30:4b:65:19:58:59

Using the CA private key and X.509 certificate we issue an ECC user certificate based on the PKCS#10 Certificate Request

# pki --issue --cacert My_ECC_CaCert.pem --cakey My_ECC_CaKey.pem --in ak_ecc_Req.pem --type pkcs10 --flag clientAuth --lifetime 1826 > ak_ecc_Cert.der

The certificate is ready to be shipped to the user

# pki --print --type x509 --in ak_ecc_Cert.der 
  subject:  "C=CH, O=Cyber, OU=user@strongswan.org"
  issuer:   "C=CH, O=Cyber, CN=My ECC CA"
  validity:  not before Oct 10 05:52:51 2022, ok
             not after  Oct 10 05:52:51 2027, ok (expires in 1825 days)
  serial:    09:12:94:3b:ce:3a:9f:f4
  altNames:  user@strongswan.org
  flags:     clientAuth 
  authkeyId: 24:be:9a:27:51:71:e4:79:63:37:a1:02:e8:51:30:4b:65:19:58:59
  subjkeyId: 52:b0:c9:b7:62:43:da:c3:b7:60:4d:d9:d2:09:5b:55:b6:a6:46:53
  pubkey:    ECDSA 384 bits
  keyid:     fa:6a:57:e1:f7:c7:c0:2e:d3:56:d6:e5:13:4f:bb:87:ea:10:a6:66
  subjkey:   52:b0:c9:b7:62:43:da:c3:b7:60:4d:d9:d2:09:5b:55:b6:a6:46:53

ECC Attestation Certificate

We again determine the exact size of the binary-encoded X.509 certificate

# ls -l ak_ecc_Cert.der 
-rw-r--r-- 1 root root 508 Oct 10 05:52 ak_ecc_Cert.der

Next we allocate 445 bytes needed by the X.509 certificate in the NV-RAM

# tpm2_nvdefine 0x01800004 -C o -s 508 -a 0x2000A
nv-index: 0x1800004

The certificate can now be stored in the NV memory under the handle 0x01800004

tpm2_nvwrite 0x01800004 -C o -i ak_ecc_Cert.der

There now two objects stored in NV-RAM

# tpm2_getcap handles-nv-index
- 0x1800003
- 0x1800004

More details on the objects stored in NV-RAM can be displayed with

# tpm2_nvreadpublic
0x1800003:
  name: 000b2a068cdb1717d19392ee7125a527064d7370b8c3a21b41327dbfe0672cf95547
  hash algorithm:
    friendly: sha256
    value: 0xB
  attributes:
    friendly: ownerwrite|policywrite|ownerread|written
    value: 0x2002000A
  size: 1098

0x1800004:
  name: 000b0a7c324108965e93c98559cc5f758739a3f4107bd85a94416fa50eb59a639724
  hash algorithm:
    friendly: sha256
    value: 0xB
  attributes:
    friendly: ownerwrite|policywrite|ownerread|written
    value: 0x2002000A
  size: 508

The pki tool can read the X.509 certificate stored in the TPM

# pki --print --type x509 --keyid 0x01800004
TPM 2.0 via TSS2 v2 available
loaded certificate from TPM NV index 0x01800004
  subject:  "C=CH, O=Cyber, OU=user@strongswan.org"
  issuer:   "C=CH, O=Cyber, CN=My ECC CA"
  validity:  not before Oct 10 05:52:51 2022, ok
             not after  Oct 10 05:52:51 2027, ok (expires in 1825 days)
  serial:    09:12:94:3b:ce:3a:9f:f4
  altNames:  user@strongswan.org
  flags:     clientAuth 
  authkeyId: 24:be:9a:27:51:71:e4:79:63:37:a1:02:e8:51:30:4b:65:19:58:59
  subjkeyId: 52:b0:c9:b7:62:43:da:c3:b7:60:4d:d9:d2:09:5b:55:b6:a6:46:53
  pubkey:    ECDSA 384 bits
  keyid:     fa:6a:57:e1:f7:c7:c0:2e:d3:56:d6:e5:13:4f:bb:87:ea:10:a6:66
  subjkey:   52:b0:c9:b7:62:43:da:c3:b7:60:4d:d9:d2:09:5b:55:b6:a6:46:53

Object Removal from Non-Volatile Memory

If an object isn't used anymore it can be removed from NV-RAM with the following command

# tpm2_nvundefine 0x01800003 -C o
# tpm2_getcap handles-nv-index
- 0x1800004

Author: Andreas Steffen CC BY 4.0