If on the one hand, the correct procedure is sign-encrypt-sign, then why, on the other hand, is the parallel not sign-hash-sign ?
--dan ============= http://world.std.com/~dtd/sign_encrypt/sign_encrypt7.ps Donald T. Davis, "Defective Sign & Encrypt in S/MIME, PKCS#7, MOSS, PEM, PGP, and XML.", Proc. Usenix Tech. Conf. 2001 (Boston, Mass., June 25-30, 2001), pp. 65-78.(180 Kbytes) (PDF, 200 Kbytes) (HTML, 80 Kbytes) Summary of the paper. Abstract: Simple Sign & Encrypt, by itself, is not very secure. Cryptographers know this well, but application programmers and standards authors still tend to put too much trust in simple Sign-and-Encrypt. In fact, every secure e-mail protocol, old and new, has codified naïve Sign & Encrypt as acceptable security practice. S/MIME, PKCS#7, PGP, OpenPGP, PEM, and MOSS all suffer from this flaw. Similarly, the secure document protocols PKCS#7, XML- Signature, and XML-Encryption suffer from the same flaw. Naïve Sign & Encrypt appears only in file-security and mail-security applications, but this narrow scope is becoming more important to the rapidly-growing class of commercial users. With file- and mail-encryption seeing widespread use, and with flawed encryption in play, we can expect widespread exposures. In this paper, we analyze the naïve Sign & Encrypt flaw, we review the defective sign/encrypt standards, and we describe a comprehensive set of simple repairs. The various repairs all have a common feature: when signing and encryption are combined, the inner crypto layer must somehow depend on the outer layer, so as to reveal any tampering with the outer layer. --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]