What's different between RSASSA and RSAPSS padding mode?

[Dr. Matthias St. Pierre]

It’s the same. The correct full name is RSASSA-PSS, where ‘SSA’ stands for Secure Signature Algorithm (IIRC) and ‘PSS’ for Probabilistic Signature Scheme

Regards

https://en.wikipedia.org/wiki/PKCS_1#Schemes
https://datatracker.ietf.org/doc/html/rfc4056



From: openssl-users <openssl-users-bounces at openssl.org> On Behalf Of Eddie Chang
Sent: Wednesday, May 12, 2021 2:46 AM
To: openssl-users at openssl.org
Subject: What's different between RSASSA and RSAPSS padding mode?

Hi:
  I'm new comer to openssl. Recently, I study SPDM document https://www.dmtf.org/sites/default/files/standards/documents/DSP0274_0.99a.pdf and feel confused about ReqBaseAsymAlg structure in page 49.
In this spec, I saw it can support RSASSA_4096 and RSAPSS_4096. But I check opensl source code,  rsa_padding_mode option only support pss padding. Don't have any idea about RSASSA.
Anyonce can please help to comemnt what different between RSASSA and RSAPSS is?

For testting, I can specify PSS padding with SHA256 digest for sign and verfiifcation as below command.
openssl dgst -sha512 -binary  -out sha512_out.bin  test.bin
openssl pkeyutl -sign -in sha512_out.bin -inkey gv100_rsa_3072_pvt_dbg.pem -out sig1.bin -pkeyopt digest:sha512 -pkeyopt rsa_padding_mode:pss -pkeyopt rsa_pss_saltlen:-1
openssl pkeyutl -verify -in sha512_out.bin -sigfile sig1.bin  -pkeyopt digest:sha512  -pkeyopt rsa_padding_mode:pss -pkeyopt rsa_pss_saltlen:-1 -pubin -inkey gv100_rsa_3072_pub_dbg.pem

But don't know how to test RSASSA.

Thanks
Byte 0 Bit 5. TPM_ALG_RSASSA_4096
Byte 0 Bit 6. TPM_ALG_RSAPSS_4096

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