It has been reported in Economic times today that the Cyber regulations
Advisory Committee is finalizing the standards for Digital Signature systems
According to the report, the Ministry of Information Technology (MIT) is
said to be considering to make it mandatory for Digital Certificates to
be issued with two sets of keys, one set for digital signature and the
other for encryption.
Readers may know that the Digital Signature system is based on the Public
Key Infrastructure system where there is a unique pair of keys consisting
of a Public and a Private key. The private key is always
held in the custody of the owner and the public key is distributed
to the intended recipient of a message and also placed in the public repository.
The unique property of these keys is that a document encrypted with
one can only be decrypted with the other and vice versa. The reliability
of this property is so well established that any document that can be decrypted
with a "Public Key of Mr X" is presumed to have been encrypted originally
only with the corresponding "Private key of Mr X".
The normal practice for affixing Digital Signatures to documents is
to follow the two step process.
Calculate a Hash Code for the document by using a standard
hash algorithm which produces a one way hash code that is unique to any
given document.
Encrypt the hash code with the private key of the key pair.
This encrypted hash code is sent to the addressee as an attachment to
the main message.
On receipt of the message with the encrypted hash code, the recipient
follows the following two step process to verify the signature.
He decrypts the hash code with the public key of the sender which confirms
the authentication process that the message has in deed been sent
by the holder of the corresponding private key.
He also recalculates the hash code of the message as received and tallies
this with the decrypted value sent to him.
(P.S:. The actual process of signing and verification is done by the
browser or the e-mail client automatically and the users only let their
systems install the keys within the applications in the first place).
The above form of digital signature not only establishes the authentication
but also the "Data Integrity" of the message during transmission since
no two documents will have the same hash code.
Encryption of the complete document can be done in addition to a affixing
of the above signature if confidentiality has to be maintained during the
transmission. Such encryption can be done either with the private key of
the originator or with the public key of the addressee. In each of these
cases, it can be decrypted with the corresponding other key of the pair.
The standard practice is to encrypt mail messages with the public key of
the recipient.
In order to also bestow the nature of "Non Repudiation" to the documents,
the system is developed on the principle that the custody of the
private key never leaves the original generator of the key pair. The copy
of the private key is therefore normally not kept even by the Certifying
Authority. If therefore, the private key is lost, it is not possible to
recover it from the Certifying Authority. Some Certifying authorities
may provide replacement of keys while some don't provide even for such
replacement.
What the Government is now proposing is that a user of the digital signature
system should hold two pairs of keys one for signing and the other for
encryption so that a copy of the "Encryption Private Key" can be mandatorily
lodged with the Certifying Authority. The need for this is to intercept
encrypted messages in case of necessity.
If this system has to be adopted, the standard Key generation and
Digital Certification software being used world wide has to be modified.
The browsers such as Netscape and Internet explorer needs to be made compatible
with the system of two sets of keys to be used during the process of transmitting
any secured message.
It appears that this intended proposal from the CRAC is not technologically
feasible without a major upheaval of the system. It has already been pointed
out by naavi.org that the ITA-2000 has the dubious distinction of defining
what was known as "Cracking "as "Hacking". Now we will have the dubious
distinction of making all the globally used browsers incompatible with
the system of Digital Signatures we are about to adopt.
There is a need to rethink on the subject.
Naavi
march 31, 2001
Report
in Economic Times
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