Frequently Asked Questions

1. Why does one need to understand public key cryptography when discussing Assure Systems' S/Mark® Product Verification System?

S/Mark® is the direct use of public key cryptography in security labeling for products. Authentication results from the information contained within the mark, and not in the physical form of the mark. An S/Mark® is a special message using cryptographic techniques.

2. What is some of the history of public key cryptography? For example, who are these fellows Diffie, Hellman, and Merkle?

Whitfield Diffie, Martin Hellman, and Ralph Merkle are computer scientists who were at Stanford and UC-Berkeley when they contributed significantly to the development of public key cryptography during the mid-70's through the early 80's.

3. What is RSA?

In the mid-70's three computer scientists at MIT developed the public key mathematical algorithm which today is the most widely used and has withstood all attacks against it. It is known as the RSA algorithm, named after the three inventors, Rivest, Shamir, and Adelman.

4. So, what makes up public key crypto technology?

A series of patents originally owned by Stanford and MIT and bearing the names of these individuals have formed the core technology which is being practiced in an ever widening range of applications primarily involving the internet and electronic commerce. An example with which the reader may already be familiar is online banking. When using a Netscape browser, the reader should notice that the key at the lefthand bottom becomes "solid" and unbroken when transacting with his/her account. This indicates that the communications are encrypted and that a secret key exchange has occurred using the public key technology described in these patents.

5. What is RSA Data Security?

RSA Data Security, Inc., founded by Rivest, Shamir, and Adelman in the early 80's, owns the commercial rights to the public key crypto patents and has built itself into the dominant provider of the underlying software technology which powers the applications mentioned above.

6. Has RSADSI been successful?

RSADSI nearly failed in its early years but became financially viable by 1986 by licensing its software for early network applications. Today it is a robust business.

7. Who is Jim Bizdos?

Jim Bizdos joined RSADSI as president in early 1986 and grew it to a size last year whereby Security Dynamics, Inc. bought it in a deal worth $400MM. This growth has paralleled the growth of the internet. Jim Bizdos has emerged as a strong spokesman for industry on the public policy issue of exporting strong encryption, and continues to manage the strategy of agressively licensing RSA technology for new, ever evolving applications.

8. How does the S/Mark® system relate to all of this?

The S/Mark® system is the first application of public key cryptography for the security of products, instead of the security of communication, and is RSADSI's first licensee for this field of use.

9. What is the S/Mark® system?

The S/Mark® system consists of a special message which is a digital signature created with the RSA algorithm and each product receives its own unique digital signature. All are different and a digital signature is never repeated.

10. How is S/Mark® used?

The special message can be read anywhere, anytime, and by anyone using a portable computer which can be made freely available, since this computer contains only the public key. It is used to read the digitally signed message and does not need to be kept secure.

11. How does public key cryptography work and how does a digital signature provide authenticity and tamperproofness?

This is answered by first considering secret key cryptography.

Modern day cryptography is based upon secret keys, not secret algorithms. (An algorithm is the recipe or formula. It is the method by which raw ingredients, for example, are converted into a cake. In the case of cryptography, a message is converted into a scrambled message through use of the algorithm.) In the old days, the algorithm was kept secret. Soon, however, the secret would normally get out and suddenly the whole system was useless. All of the algorithm "machines" used to encrypt and decrypt messages, for example, now needed to be replaced with machines that would implement a new, secret algorithm.

After WWII, secret key cryptography was invented using mathematics involving large random numbers which are used as keys. Anyone can know the mathematical algorithm which encrypts a message using a key, but without knowing the key no one can decrypt the scrambled message. Since the key is a large number randomly chosen and kept secret, it is infeasible for someone to unscramble the message even by trying all possible keys. There are just too many for even the most powerful of computers to try.

Thus the security of the system rests with the key, not the algorithm. If an adversary learned the secret key, one merely needs to change the key to a new number. This new number, or key, is distributed in a secure manner to valid users. It is not necessary to come up with a new "algorithm machine". This is quite a remarkable improvement over the old system of secret algorithms. It is quite simple to generate random numbers at will.

Note, however, that keys must be securely distributed and kept secret. Only trusted parties can have keys, and with many keys out in distribution, the chance that an adversary acquires one increases.

12. How is public key cryptography different?

Public key cryptography is a remarkable solution to this last problem concerning key distribution. There are branches of mathematics, discovered by the scientists named above, that provide for two mathematically related keys where when one key is used to encrypt a message, then only the other one can decrypt the message. And, if only one key is known, it is infeasible for anyone to mathematically derive the other key. Thus, the known key is public, while the other is kept secret and is called the private key.

So, how does this work? Suppose everyone who wants to send secure messages to each other creates for themselves one of these key pairs. Each keeps one key private and publishes the other key to everyone else. Each person with a key pair instructs everyone who wants to send a secure message to him to encrypt the message with his public key. When the message is received, this person is the only one who can read the message using his private key, so long as he keeps his private key secret.

Public key cryptography thus solves the key distribution problem. The public key can be freely distributed and adversaries cannot use it to read encrypted messages intended only for the eyes of the private key holder.

13. What are digital signatures?

There is one more important thing that one can do with public key cryptography. Since a person keeps his private key secret and only he possesses it, only he can encrypt messages with it. Everyone who has his public key can decrypt the message and read it. Everyone knows that this message can only come from the owner of the private key. Otherwise, the public key would not decrypt the message into anything which is readable. This message is considered to by "digitally signed". Furthermore, the content of the message cannot be changed by someone who intercepts it. The adversary may read the message using the public key which is freely available, but has no way of changing it and re-encrypting it because the adversary does not have the original private key. Thus, the message is tamperproof.

So, the private key holder can send tamperproof messages which are proven authentic to the receiving party by virtue that his public key successfully decrypts the digitally signed message.

14. So, S/Mark® is a digital signature?

Yes. It is this last protocol which Assure Systems uses as the basis for its S/Mark® system. Assure Systems creates a public key pair unique to a manufacturer, creates individual messages for each of the manufacturer's products, digitally signs each message with the private key, provides for the digital signatures to be marked on the product in the form of a 2D bar code, and provides the public key and S/Mark® software running on portable data terminals so the digital signatures can be inspected anytime and anywhere. Successful reading of the message proves each digital signature belongs to the manufacturer as certified originally by Assure Systems and has not been tampered with.

15. Compare the S/Mark® to an authenticating hologram. How are they the same and how are they different?

For a hologram, the embossing plates used to make it are kept private on behalf of the manufacturer. Field inspection of the hologram on the product provides evidence of authenticity so long as the plates used to make it have been kept secure. Similarly, field inspection of the message decrypted from a S/Mark® digital signature provides evidence of authenticity so long as the private key used to make it is kept private and secure.

However, the similarity ends at this point and the differences are remarkable. While all holograms are mass produced to be identically the same, S/Marks® are produced to be uniquely different from one another in all instances. No two are alike.

Any duplicates of S/Marks® are evidence of counterfeiting and field inspection software detects this. Counterfeiters cannot mass produce valid S/Marks® without knowing the private, secret key. On the other hand, if a counterfeiter makes good copies of the hologram embossing plates, he is positioned to mass produce hard to detect fake holograms.

The last difference between S/Marks® and holograms is an important one. The S/Mark, being a purely information containing mark, can encapsulate product information and tracking information in a way that is both hidden and tamperproof. So, in one mark both authentication and information-bearing functions are combined.

16. What is required to obtain S/Marks® and apply them to product packaging or labels?

Assure Systems uses a proprietary software program which it runs on a secure host computer. This software program is call S/MarkManager and it was built using the underlying software code licensed from RSADSI. Assure Systems uses this software to create the public key pair for the manufacturer, and then uses the private key to create digital signatures. The file of S/Mark digital signatures is securely delivered by Assure Systems to the print engine of a package printer or label converter which then prints these signatures as a 2D bar code. Once the bar codes are on the product packages and the product distributed, this step in the process is finished.

17. How are S/Marks® inspected in the field?

There are two approaches. If the inspection is remote, that is, a network connection is not available, then a proprietary software program called S/MarkInspector runs on a portable data terminal with an integrated bar code reader. S/MarkInspector uses the stored public key corresponding to the manufacturer's digital signatures to decrypt them to determine their authenticity. If a network connection is available, then any bar code imager connected to a PC can upload the inspected S/Marks® to an Assure Systems' server where a complete authenticity check takes place.

18. What do you mean by "complete authenticity check"?

In the first case the portable data terminals do more than just read S/Marks®. They capture this data in a file for later uploading to an Assure Systems' server for consolidation and reporting. These terminals remember what they inspect and try to find duplicate occurrences of S/Marks®, which would indicate counterfeiting. When later uploaded, the server conducts a similar duplicate check but over a much greater base of inspected S/Marks® assembled from previous uploading activity. In the case where inspection occurs with a real time connection to the server, all of this activity takes place in an instant on the server.