ST33TPHF20SPI datasheet(39/47 Pages) STMICROELECTRONICS

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FIPS140-2 SECURITY POLICY

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integrity

FW integrity is verified by computing an EDC (CRC-16 ISO 13239) and comparing it to

reference values. FW integrity is verified during boot sequence before execution of one of

the code block (CML, AFL and TPM) and during full self-tests execution. If failure is

detected during boot sequence, TPM enters an infinite reset loop that can be exit only by

power-off/power-on sequence. In failure is detected during self-tests, status is set to FAIL

and error is returned.

integrity

HW integrity is guaranteed via check of HW sensors. If failure is detected during boot

sequence, status is set to FAIL and error is returned.

4.2

Asymmetric cryptography self-tests list

Table 22 : Asymmetric cryptography self-tests list

Algorithm

tested

Test description

RSA

A known key is loaded (2048 bits length). Signature RSASSA-PKCS1-v1_5 is generated

on known data (20 bytes). Output of signature is compared to a reference signature.

Signature verification is performed on the generated signature.

ECDH

A known private key d (32 bytes length) is used with a known point P of NIST P-256

curve to compute P = dQ. Q is compare to known reference point.

ECDSA

A known private key (256 bits) is used to generate ECDSA signature based on NIST P-

256 curve. Output of signature is compared to a reference signature. Signature

verification is performed on the generated signature.

4.3

Conditional tests list

Table 23 : TPM conditional tests

Algorithm tested

Test description

FW integrity

FW integrity is verified by computing an EDC (CRC-16 ISO 13239) and comparing it

to reference values.

Hash-DRBG

Each 32 bytes of generated data are compared to the previous generated data. If

data are equal, status is set to FAIL and error is returned.

NDRNG

TPM performs AIS31 statistical test verification on NDRNG output and continuous

HW self-tests (AS09.42) on NDRNG 48-bits output sequence. If test fails, TRNG_ERR

bit is raised in SEC_STAT register. Status is set to FAIL and error is returned.

FW load

During field upgrade procedure, several checks are performed before authorizing

the FW to be upgraded:

Verification of signature (RSASSA-PSS) on the first data blob to ensure

authentication of the FW

Verification of digest (SHA256) on each subsequent blob to guarantee

integrity of the full FW.

RSA key

generation

A new RSA key is generated or retrieved from pre-computed keys (done in BKG).

Depending on the key purpose (signing or encrypting) indicated in sign attribute of

the key, en/decryption or signing/verification is done on known data (16 bytes).

ECC key

generation

On each ECC key generation, an ECDSA signature is generated and verified on

curve NIST P-256.

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