On 9/23/21 22:11, Mandava, Sreevidya wrote:
Attached my certs.

Details for your certificates:

Certificate type: RSA 2048-bit
Signature algorithm: sha256WithRSAEncryption

This is a self-signed certificate.

Certificate type: EC curve=prime256v1
Signature algorithm: sha256WithRSAEncryption

So yes, you are indeed using an EC key with an RSA signature. Uncommon, but certainly not impossible.

The error message they were getting were "unsupported signature algorithm ecdsa_sha1". Unfortunately don't have the logs and can't
paste the actual client cert. I only have a packet capture during the
failure and I was comparing tomcat logs from successful case and the
packet capture from failure case. I noticed that the only difference
is when the tomcat is requesting for client certificate it is sending
list of acceptable/supported certificate types and signature
algorithms. I am trying to understand where tomcat gets those values
from? We don't enable/disable any signature algorithms  in our or java.policy files or in Catalina.policy files. The
only place we specify any ciphers is in our connector
(connector.txt). How does tomcat determine what to send as an
acceptable/supported certificate type or signature algorithm?
I don't see any ECDSA_SHA1 in use in the certs themselves. Perhaps the problem is some algorithm chosen at runtime? ECDSA_SHA1 might be chosen as a part of the cipher suite chosen by the server.

What version of Java are you using?

Here is your connector (minus some irrelevant info):

<Connector scheme="https"


Are you using the "rsatestca" certificate for your server, or something else? You have only enabled RSA cipher suites. I'm not sure what that will do when you have a mixed-key-type certificate chain for the client-certificate.

Is there any particular reason why you are using RSA for the CA and EC for the client-cert?


-----Original Message-----
From: Christopher Schultz <>
Sent: Wednesday, September 22, 2021 6:16 PM
Subject: {EXTERNAL} Re: Supported signature algorithms in Tomcat 8.5

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On 9/22/21 12:25, Mandava, Sreevidya wrote:
Tomcat version : 8.5.70

Attached my self -signed client cert(ecdsatestclient.crt_txt), self
signed CA (rsatestca_original.crt_txt)output from openssl
(defaultciphersuite.txt) my connector configuration(connector.txt)

Your attachment has been stripped. Please copy/paste your certificate in 
PEM-encoded-DER format (i.e. -----BEGIN CERTIFICATE-----) into the body of your 

Problem: We have a client that is connecting to tomcat with an ECC
cert signed by a RSA signer.

That would be a very odd configuration indeed.

Client authentication is enabled in tomcat. They are seeing handshake
failures in ClientKeyExchange/Certificate Verify stage.
Do you have a specific error message and/or stack trace?

Why is there difference between the "certificate types" and "signature
algorithms"? Where/how  does tomcat get the values for "certificate
types" and "supported signature algorithms"?
Certificate types are usually "RSA" or "EC" (or maybe "DSA") and sometimes just, 
generically, X.509. Signature algorithms are typically things like "sha256withRSAencryption", etc.

Having the certificate itself would be very helpful in trying to debug this 


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