"XML Signature Syntax and Processing (XMLDsig) is a W3C recommendation for providing integrity, message authentication, and/or signer authentication services for data. XMLDsig is commonly used by web services such as SOAP. The XMLDsig recommendation includes support for HMAC truncation, as specified in RFC2104. However, the XMLDsig specification does not follow the RFC2104 recommendation to not allow truncation to less than half of the length of the hash output or less than 80 bits. When HMAC truncation is under the control of an attacker this can result in an effective authentication bypass. For example, by specifying an HMACOutputLength of 1, only one bit of the signature is verified. This can allow an attacker to forge an XML signature that will be accepted as valid." - http://www.kb.cert.org/vuls/id/466161
More information at: HMAC truncation in XML Signature: When Alice didn't look. - http://www.w3.org/QA/2009/07/hmac_truncation_in_xml_signatu.html -- Leandro Federico Meiners --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to majord...@metzdowd.com