RSA PSS security advantage











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To my humble opinion, please correct me if I'm wrong, RSA-PSS (PKCS#1 ver 2.1) advantage over RSA as described in PKCS#1 ver. 1.5 is in its security proofs. Does this proof and the advantage is still there even if the "salt" in the RSA-PSS scheme is constant over all messages, or it conditioned in generating a random salt each and every signature? That is, does the security proof of RSA-PSS assumes random salt over messages?










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  • Related to Why use randomness in digital signature algorithms?.
    – fgrieu
    Dec 3 at 11:46















up vote
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To my humble opinion, please correct me if I'm wrong, RSA-PSS (PKCS#1 ver 2.1) advantage over RSA as described in PKCS#1 ver. 1.5 is in its security proofs. Does this proof and the advantage is still there even if the "salt" in the RSA-PSS scheme is constant over all messages, or it conditioned in generating a random salt each and every signature? That is, does the security proof of RSA-PSS assumes random salt over messages?










share|improve this question






















  • Related to Why use randomness in digital signature algorithms?.
    – fgrieu
    Dec 3 at 11:46













up vote
5
down vote

favorite
2









up vote
5
down vote

favorite
2






2





To my humble opinion, please correct me if I'm wrong, RSA-PSS (PKCS#1 ver 2.1) advantage over RSA as described in PKCS#1 ver. 1.5 is in its security proofs. Does this proof and the advantage is still there even if the "salt" in the RSA-PSS scheme is constant over all messages, or it conditioned in generating a random salt each and every signature? That is, does the security proof of RSA-PSS assumes random salt over messages?










share|improve this question













To my humble opinion, please correct me if I'm wrong, RSA-PSS (PKCS#1 ver 2.1) advantage over RSA as described in PKCS#1 ver. 1.5 is in its security proofs. Does this proof and the advantage is still there even if the "salt" in the RSA-PSS scheme is constant over all messages, or it conditioned in generating a random salt each and every signature? That is, does the security proof of RSA-PSS assumes random salt over messages?







rsa signature salt digital






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asked Dec 3 at 11:20









Evgeni Vaknin

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  • Related to Why use randomness in digital signature algorithms?.
    – fgrieu
    Dec 3 at 11:46


















  • Related to Why use randomness in digital signature algorithms?.
    – fgrieu
    Dec 3 at 11:46
















Related to Why use randomness in digital signature algorithms?.
– fgrieu
Dec 3 at 11:46




Related to Why use randomness in digital signature algorithms?.
– fgrieu
Dec 3 at 11:46










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Even if we make RSASSA-PSS deterministic by fixing its seed, it remains with a security proof in the Random Oracle Model per Full Domain Hashing (Jean-Sébastien Coron, On the Exact Security of Full Domain Hashing, in proceedings of Crypto 2000). We can't say the same for RSASSA-PKCS1-v1_5, because a lot of the message representative is fixed.



In practice, a better argument to use deterministic RSASSA-PSS rather than RSASSA-PKCS1-v1_5 is that vulnerable implementations of verification of RSASSA-PKCS1-v1_5 abound, when I know no vulnerable implementation of RSASSA-PSS verification (regardless of randomization), and this is less likely to happen accidentally.



However a practical argument against RSASSA-PSS is that it requires careful specification of the hash and the mask generation function: even if the later is almost universally MGF1, that could be with another hash (e.g. stuck to SHA-1) depending on implementations.






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  • 1




    Could you give an example on how RSASSA-PKCS1-v1_5 is vulnerable and an example? Or should I ask this in a separate question? Maarten.
    – Maarten Bodewes
    Dec 4 at 14:46










  • @Maarten Bodewes: RSASSA-PKCS1-v1_5 as specified has no known vulnerability. Some incorrect implementations of its signature verification step are vulnerable. Example among dozens: CVE-2014-9934. For something more detailed, a questions seems in order, but I do not know if it is for crypto.se or security.se.
    – fgrieu
    Dec 4 at 14:55












  • Yeah, if you skip validating the padding in its entirety then it may be vulnerable :P The incompetence of some people in the field is just astonishing. Goodness gracious. Thanks anyway. I'll leave it at that.
    – Maarten Bodewes
    Dec 4 at 15:13













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1 Answer
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1 Answer
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active

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up vote
4
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Even if we make RSASSA-PSS deterministic by fixing its seed, it remains with a security proof in the Random Oracle Model per Full Domain Hashing (Jean-Sébastien Coron, On the Exact Security of Full Domain Hashing, in proceedings of Crypto 2000). We can't say the same for RSASSA-PKCS1-v1_5, because a lot of the message representative is fixed.



In practice, a better argument to use deterministic RSASSA-PSS rather than RSASSA-PKCS1-v1_5 is that vulnerable implementations of verification of RSASSA-PKCS1-v1_5 abound, when I know no vulnerable implementation of RSASSA-PSS verification (regardless of randomization), and this is less likely to happen accidentally.



However a practical argument against RSASSA-PSS is that it requires careful specification of the hash and the mask generation function: even if the later is almost universally MGF1, that could be with another hash (e.g. stuck to SHA-1) depending on implementations.






share|improve this answer



















  • 1




    Could you give an example on how RSASSA-PKCS1-v1_5 is vulnerable and an example? Or should I ask this in a separate question? Maarten.
    – Maarten Bodewes
    Dec 4 at 14:46










  • @Maarten Bodewes: RSASSA-PKCS1-v1_5 as specified has no known vulnerability. Some incorrect implementations of its signature verification step are vulnerable. Example among dozens: CVE-2014-9934. For something more detailed, a questions seems in order, but I do not know if it is for crypto.se or security.se.
    – fgrieu
    Dec 4 at 14:55












  • Yeah, if you skip validating the padding in its entirety then it may be vulnerable :P The incompetence of some people in the field is just astonishing. Goodness gracious. Thanks anyway. I'll leave it at that.
    – Maarten Bodewes
    Dec 4 at 15:13

















up vote
4
down vote













Even if we make RSASSA-PSS deterministic by fixing its seed, it remains with a security proof in the Random Oracle Model per Full Domain Hashing (Jean-Sébastien Coron, On the Exact Security of Full Domain Hashing, in proceedings of Crypto 2000). We can't say the same for RSASSA-PKCS1-v1_5, because a lot of the message representative is fixed.



In practice, a better argument to use deterministic RSASSA-PSS rather than RSASSA-PKCS1-v1_5 is that vulnerable implementations of verification of RSASSA-PKCS1-v1_5 abound, when I know no vulnerable implementation of RSASSA-PSS verification (regardless of randomization), and this is less likely to happen accidentally.



However a practical argument against RSASSA-PSS is that it requires careful specification of the hash and the mask generation function: even if the later is almost universally MGF1, that could be with another hash (e.g. stuck to SHA-1) depending on implementations.






share|improve this answer



















  • 1




    Could you give an example on how RSASSA-PKCS1-v1_5 is vulnerable and an example? Or should I ask this in a separate question? Maarten.
    – Maarten Bodewes
    Dec 4 at 14:46










  • @Maarten Bodewes: RSASSA-PKCS1-v1_5 as specified has no known vulnerability. Some incorrect implementations of its signature verification step are vulnerable. Example among dozens: CVE-2014-9934. For something more detailed, a questions seems in order, but I do not know if it is for crypto.se or security.se.
    – fgrieu
    Dec 4 at 14:55












  • Yeah, if you skip validating the padding in its entirety then it may be vulnerable :P The incompetence of some people in the field is just astonishing. Goodness gracious. Thanks anyway. I'll leave it at that.
    – Maarten Bodewes
    Dec 4 at 15:13















up vote
4
down vote










up vote
4
down vote









Even if we make RSASSA-PSS deterministic by fixing its seed, it remains with a security proof in the Random Oracle Model per Full Domain Hashing (Jean-Sébastien Coron, On the Exact Security of Full Domain Hashing, in proceedings of Crypto 2000). We can't say the same for RSASSA-PKCS1-v1_5, because a lot of the message representative is fixed.



In practice, a better argument to use deterministic RSASSA-PSS rather than RSASSA-PKCS1-v1_5 is that vulnerable implementations of verification of RSASSA-PKCS1-v1_5 abound, when I know no vulnerable implementation of RSASSA-PSS verification (regardless of randomization), and this is less likely to happen accidentally.



However a practical argument against RSASSA-PSS is that it requires careful specification of the hash and the mask generation function: even if the later is almost universally MGF1, that could be with another hash (e.g. stuck to SHA-1) depending on implementations.






share|improve this answer














Even if we make RSASSA-PSS deterministic by fixing its seed, it remains with a security proof in the Random Oracle Model per Full Domain Hashing (Jean-Sébastien Coron, On the Exact Security of Full Domain Hashing, in proceedings of Crypto 2000). We can't say the same for RSASSA-PKCS1-v1_5, because a lot of the message representative is fixed.



In practice, a better argument to use deterministic RSASSA-PSS rather than RSASSA-PKCS1-v1_5 is that vulnerable implementations of verification of RSASSA-PKCS1-v1_5 abound, when I know no vulnerable implementation of RSASSA-PSS verification (regardless of randomization), and this is less likely to happen accidentally.



However a practical argument against RSASSA-PSS is that it requires careful specification of the hash and the mask generation function: even if the later is almost universally MGF1, that could be with another hash (e.g. stuck to SHA-1) depending on implementations.







share|improve this answer














share|improve this answer



share|improve this answer








edited Dec 3 at 12:08

























answered Dec 3 at 12:03









fgrieu

77.4k7160326




77.4k7160326








  • 1




    Could you give an example on how RSASSA-PKCS1-v1_5 is vulnerable and an example? Or should I ask this in a separate question? Maarten.
    – Maarten Bodewes
    Dec 4 at 14:46










  • @Maarten Bodewes: RSASSA-PKCS1-v1_5 as specified has no known vulnerability. Some incorrect implementations of its signature verification step are vulnerable. Example among dozens: CVE-2014-9934. For something more detailed, a questions seems in order, but I do not know if it is for crypto.se or security.se.
    – fgrieu
    Dec 4 at 14:55












  • Yeah, if you skip validating the padding in its entirety then it may be vulnerable :P The incompetence of some people in the field is just astonishing. Goodness gracious. Thanks anyway. I'll leave it at that.
    – Maarten Bodewes
    Dec 4 at 15:13
















  • 1




    Could you give an example on how RSASSA-PKCS1-v1_5 is vulnerable and an example? Or should I ask this in a separate question? Maarten.
    – Maarten Bodewes
    Dec 4 at 14:46










  • @Maarten Bodewes: RSASSA-PKCS1-v1_5 as specified has no known vulnerability. Some incorrect implementations of its signature verification step are vulnerable. Example among dozens: CVE-2014-9934. For something more detailed, a questions seems in order, but I do not know if it is for crypto.se or security.se.
    – fgrieu
    Dec 4 at 14:55












  • Yeah, if you skip validating the padding in its entirety then it may be vulnerable :P The incompetence of some people in the field is just astonishing. Goodness gracious. Thanks anyway. I'll leave it at that.
    – Maarten Bodewes
    Dec 4 at 15:13










1




1




Could you give an example on how RSASSA-PKCS1-v1_5 is vulnerable and an example? Or should I ask this in a separate question? Maarten.
– Maarten Bodewes
Dec 4 at 14:46




Could you give an example on how RSASSA-PKCS1-v1_5 is vulnerable and an example? Or should I ask this in a separate question? Maarten.
– Maarten Bodewes
Dec 4 at 14:46












@Maarten Bodewes: RSASSA-PKCS1-v1_5 as specified has no known vulnerability. Some incorrect implementations of its signature verification step are vulnerable. Example among dozens: CVE-2014-9934. For something more detailed, a questions seems in order, but I do not know if it is for crypto.se or security.se.
– fgrieu
Dec 4 at 14:55






@Maarten Bodewes: RSASSA-PKCS1-v1_5 as specified has no known vulnerability. Some incorrect implementations of its signature verification step are vulnerable. Example among dozens: CVE-2014-9934. For something more detailed, a questions seems in order, but I do not know if it is for crypto.se or security.se.
– fgrieu
Dec 4 at 14:55














Yeah, if you skip validating the padding in its entirety then it may be vulnerable :P The incompetence of some people in the field is just astonishing. Goodness gracious. Thanks anyway. I'll leave it at that.
– Maarten Bodewes
Dec 4 at 15:13






Yeah, if you skip validating the padding in its entirety then it may be vulnerable :P The incompetence of some people in the field is just astonishing. Goodness gracious. Thanks anyway. I'll leave it at that.
– Maarten Bodewes
Dec 4 at 15:13




















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