AM2634: RSA sign and verify

Shine

Part Number: AM2634

Hello Champs,

The RSA signature/verify example for AM2634 uses openssl rsautl -sign (raw RSA PKCS#1v1.5 signature. sign directly to hash); however, customer used openssl dgst -sign (see note: RSA PKCS#1v1.5 signature, place hash in DigestInfo before signing DigestInfo), the difference between the two signing methods is explained in the following two URLs. He looked at some information and said that openssl rsautl -sign can be considered a variant, openssl dgst -sign is a more standard way to implement openssl dgst -sign.

Example: Dthe_rsa_signing_verification_am263x-cc_r5fs0-0_normos_ti-arm-clang

The difference between the two types of signature is described at:
crypto.stackexchange.com/.../differences-between-two-rsa-signatures-using-openssl
stackoverflow.com/.../difference-between-openssl-rsautl-and-dgst

Thanks
Regards
Shine

over 1 year ago

0 Aakash Kedia over 1 year ago

TI__Mastermind 26145 points

Hi Shine,

The driver documentation clearly calls out that the requirement of the input message is to be Crypto hash with padding - https://software-dl.ti.com/secure/software/sitara-sec/AM263X-RESTRICTED-SECURITY/TIFS_MCU/zlatest/tifs_am263x_latest_docs_only/docs/api_guide_am263x/html/DRIVER_DTHE_PKA.html?__gda__=1709561939_7c5cca29616984f3994b902bf6ac2fae#autotoc_md123

We do not expect the digest Info from this method that needs to be verified. Can you be specific on the ask here ?

Best Regards,
Aakash

0 ?? ? over 1 year ago

Prodigy 65 points

I know, you use sign and verify like openssl : rsautl -sign -inkey privateKey.pem -in sha256.dgt -out sha256_signed.dgt; But we need sign and verify like openssl: openssl dgst -sha256 -sign privateKey.pem -out sign.bin msg.bin. Therefore, I want know What's the difference "rsautl -sign" openssl command and "dgst -sign" openssl command? How can I modify the C code to achieve the "dgst -sign" openssl command?

0 Aakash Kedia over 1 year ago in reply to ?? ?

TI__Mastermind 26145 points

Hi Shine,

?? ? said:
Therefore, I want know What's the difference "rsautl -sign" openssl command and "dgst -sign" openssl command?

In the link provided it clearly calls out that dgst-sign contains the digest information and it is expected that the hashing operation is called as part of the PKA call where the hash digest is also part of the same.

?? ? said:
How can I modify the C code to achieve the "dgst -sign" openssl command?

Let me check if the modifications are really possible or not. These are mostly goverened by PKA firmware. I need to check if according to the spec sheet, if the firmware supports the same or not.

Best Regards,
Aakash

0 Aakash Kedia over 1 year ago in reply to Aakash Kedia

TI__Mastermind 26145 points

Hi Shine,

The firmware does not support any ASN1 parsing hence, this needs to be handled by the application software. Implement the ASN1 parsing logic, generate the hash using the DTHE-SHA and then use RSA sign to generate the signature on your required configuration.

Best Regards,
Aakash

0 ?? ? over 1 year ago in reply to Aakash Kedia

Prodigy 65 points

Hi, Aakash,

this picture is the RSA sign and verify example from TI.It also shall use DTH-SHA to generate the hash value(sha256() function), then generate the signature.the gPkaRsaVerifyOutputResult is same as "openssl rsautl -verify" command.

You means that if I want to implement "openssl dgst", I can't use sha256() function,I need to achieve the hash value implement ASN1 through the software, right? I can't know the details the two kinds hash digest, whether you can provide some help for me?

Best Regards,

Zhou,

0 Aakash Kedia over 1 year ago in reply to ?? ?

TI__Mastermind 26145 points

Hi Zhou,

You need to follow the steps mentioned in this link - https://datatracker.ietf.org/doc/html/rfc8017#section-9.2

Best Regards,
Aakash

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AM2634: RSA sign and verify