Para obtener metadatos de una fuente remota, definí unExtendedMetadataDelegate frijol de la siguiente manera:

@Bean
@Qualifier("replyMeta")
public ExtendedMetadataDelegate replyMetadataProvider() throws MetadataProviderException {
    String metadataURL = "https://ststest-replynet.reply.it/FederationMetadata/2007-06/FederationMetadata.xml";
    final Timer backgroundTaskTimer = new Timer(true);
    HTTPMetadataProvider provider = new HTTPMetadataProvider(
            backgroundTaskTimer, httpClient(), metadataURL);
    provider.setParserPool(parserPool());
    ExtendedMetadataDelegate emd = new ExtendedMetadataDelegate(
            provider, new ExtendedMetadata());
    return emd;
}

Para garantizar el establecimiento de la confianza de firma, agregué la clave relacionada tanto en el almacén de claves JDK como en el almacén de claves de la aplicación (el segundo paso podría no ser suficiente); a pesar de eso, se produce un error al ejecutar la aplicación web.

[2014-08-18 14:36:47.200] boot - 6000 DEBUG [localhost-startStop-1] --- SignatureValidator: Attempting to validate signature using key from supplied credential
[2014-08-18 14:36:47.200] boot - 6000 DEBUG [localhost-startStop-1] --- SignatureValidator: Creating XMLSignature object
[2014-08-18 14:36:47.206] boot - 6000 DEBUG [localhost-startStop-1] --- SignatureValidator: Validating signature with signature algorithm URI: http://www.w3.org/2001/04/xmldsig-more#rsa-sha256
[2014-08-18 14:36:47.207] boot - 6000 DEBUG [localhost-startStop-1] --- SignatureValidator: Validation credential key algorithm 'RSA', key instance class 'sun.security.rsa.RSAPublicKeyImpl'
[2014-08-18 14:36:47.329] boot - 6000 DEBUG [localhost-startStop-1] --- SignatureValidator: Signature validated with key from supplied credential
[2014-08-18 14:36:47.329] boot - 6000 DEBUG [localhost-startStop-1] --- BaseSignatureTrustEngine: Signature validation using candidate credential was successful
[2014-08-18 14:36:47.330] boot - 6000 DEBUG [localhost-startStop-1] --- BaseSignatureTrustEngine: Successfully verified signature using KeyInfo-derived credential
[2014-08-18 14:36:47.330] boot - 6000 DEBUG [localhost-startStop-1] --- BaseSignatureTrustEngine: Attempting to establish trust of KeyInfo-derived credential
[2014-08-18 14:36:47.330] boot - 6000 DEBUG [localhost-startStop-1] --- BasicX509CredentialNameEvaluator: Supplied trusted names are null or empty, skipping name evaluation
[2014-08-18 14:36:47.331] boot - 6000 DEBUG [localhost-startStop-1] --- MetadataCredentialResolver: Attempting PKIX path validation on untrusted credential: [subjectName='CN=ADFS Signing - ststest-replynet.reply.it']
[2014-08-18 14:36:47.346] boot - 6000 ERROR [localhost-startStop-1] --- MetadataCredentialResolver: PKIX path construction failed for untrusted credential: [subjectName='CN=ADFS Signing - ststest-replynet.reply.it']: unable to find valid certification path to requested target
[2014-08-18 14:36:47.347] boot - 6000 DEBUG [localhost-startStop-1] --- PKIXSignatureTrustEngine: Signature trust could not be established via PKIX validation of signing credential
[2014-08-18 14:36:47.347] boot - 6000 DEBUG [localhost-startStop-1] --- BaseSignatureTrustEngine: Failed to establish trust of KeyInfo-derived credential
[2014-08-18 14:36:47.347] boot - 6000 DEBUG [localhost-startStop-1] --- BaseSignatureTrustEngine: Failed to verify signature and/or establish trust using any KeyInfo-derived credentials
[2014-08-18 14:36:47.347] boot - 6000 DEBUG [localhost-startStop-1] --- PKIXSignatureTrustEngine: PKIX validation of signature failed, unable to resolve valid and trusted signing key
[2014-08-18 14:36:47.347] boot - 6000 ERROR [localhost-startStop-1] --- SignatureValidationFilter: Signature trust establishment failed for metadata entry http://ststest-replynet.reply.it/adfs/services/trust
[2014-08-18 14:36:47.349] boot - 6000 ERROR [localhost-startStop-1] --- AbstractReloadingMetadataProvider: Error filtering metadata from https://ststest-replynet.reply.it/FederationMetadata/2007-06/FederationMetadata.xml
org.opensaml.saml2.metadata.provider.FilterException: Signature trust establishment failed for metadata entry

El error desaparece al configurar:

emd.setMetadataTrustCheck(false); 

... pero me gustaría verificar los metadatos usados.

¿Hay alguna manera de resolver este error?

Actualizar:

Traté de configurar elExtendedMetadata como sigue pero el error persiste.

em.setAlias("defaultAlias");
em.setSigningKey("*.reply.it (Go Daddy Secure Certification Authority)");