Asymmetric and Symmetric key
Project goals
Symmetric and asymmetric keying system applies different methods of revoking and provision of security to documents sent over a medium. Users should be able to trust the mode of sending data over a medium as well as its integrity must be ensured. Any manner of insecure data use may proof to be a liability and consequently an inefficient mode to be desired. The public operations creates a manner in which one way functions are created, a person is hence able to perform operations like the encryption or otherwise the verification of signatures. This may however be hard to accomplish the inversion that may involve decryption or otherwise the creation of the signature which is done without the provision of the whole information. The private key is needed for the inversion operations with private key.
Symmetric is applied for encryption as mentioned; examples are like the RC4 as well as Data Encryption Standard (DES). The can also be combination of the private and the public key to acquire the benefits accrued to them. The protocols are TLS, SSL, and IPsec among others.
When it comes to encryption of the information, the message is encrypted and when this is done it becomes quite difficult to return it to its initial form. This may only be done through the use of a key. The text is in composition of ASCII text, a database file among other forms of data. Encryption is done in the initial form when sending the message and decryption is done when it has already been received. It is then received in its original form.
The encryption mentioned prevents the message from being accessed by anyone else except the holder of the key. On the other hand, there is the digital signature which is used when one needs to send messages to a number of people in plain text form. This method is set to acknowledge that the message has been sent by the sender and no form of tampering has been performed onto the message. The digital signatures are produced using the public key signature method while the private key creates the signature.
Hashing is still another way of enhancing security, it is a one-way function. With the knowledge of the hash of a document it is hard to produce another document. A digital signature is hash encrypted using a private key. Its verification is done using public signature and matching it alongside the hashed document. The strength of the hash is quite important and is dependent on the quality of the hash function.
Certificates are documents are normally a third party which is reliant on the verification on the matching of the public keys. Their benefits is when two individuals place their trust in the certificate authority any manner of exchanging the certificates accrues to the learning of the other party’s public keys and apply them to encrypt data and send it to another person or otherwise its verification.
The life time of certificates are however limited, once created and sent on request and revoked when compromised or otherwise expired. Revocation is necessary and is sent to another key or another person. Revocation is done when a certificate is used inappropriately, and fraud among others.
Background, practical investigation and analysis
Symmetric encryption which is otherwise called public keying, is an algorithmic tool that makes it possible for people to pass secret information in an open form of communication media which accessible to others to listen to. This is made possible through the application of a shared secret randomness known otherwise as a key (et al, 1997: Rhee, M. Y., 1994). It is applied in use for encryption and decryption; instances of it are Data Encryption Standard which is extended as the triple DES and DES-X, IDEA, SAFER and AES among others. Symmetric keying uses the same key both for encryption and decryption.
The exchange that occurs in the symmetric keys is normally a problem as the secrecy of the transferred data is dependent more so on the secrecy of the key. Any change done is to enable their discovery, it hence has to be done often and securely done.
On the other hand asymmetric algorithms apply the use of a pairs of keys where one is used for encryption and the other one for decryption. It is otherwise called private key in the sense that it is placed secretly. All those who are in possession of the public key have the ability to send encrypted messages to the destined person of the secret key. It cannot be modeled out from the public key.
The present world is quite applicable to the use of the asymmetric key, this is cause it has no sharing mechanisms hence the risks that are in place of being known are minimized. Of the two keys, a user needs to place one of them in secrecy in addition to the public keys which should not be changed. With Symmetric keys require that each user must have an own shared key. Examples of asymmetric key are RSA, DSA, and ELGAMAL. Asymmetric algorithm is computational in contrast to the symmetric method.
Asymmetric keying is however a slower method in comparison to symmetric keying which is faster. This has consequently led to the combination of the two methods so as to improve performance. The asymmetric keys are more relevantly used for granting access through authentication it then follows a single or more keys are produced and exchanged using the asymmetric encryption (Kurt Garloff, 2000). It is in this form that the two methods are applied. Instances of this process are RSA/IDEA combination of the PGP2 which is used by GnuPG.
In terms of security, the symmetric keying is by far the most secure when a comparison is done with the symmetric keying. The asymmetric method has broken security and the ones not broken. Care must however be taken when handling this algorithms.
The management of the keys takes into play several things; the generation of the key, the transit of the key, its application and finally its destruction. The levels of the key consist of several stages each with a close relation to the other. The revocation of the key placed between its usage as well as the destruction of the procedure, this is because the revocation of the key must be stopped due to the compromise brought forth as well as limited confidentiality. Moreover, the revocation of the key may consist of some effects which are dependent upon the delivery to the various crypto-systems. “The strength of any cryptographic system rests with the key distribution technique” (W. Stalling 1995). To expound on this, it means that the cryptography systems are relevant to uphold the revocation of the key therefore meaning that the revocation of the key is variable.
This paper aims to focus in not a lengthy form the methods used when distributing a key symmetrically and asymmetrically. The algorithms will result to an analysis of the revocation process.
According to Grover 1990, the cryptography is more reliant upon the distribution of the keys. The key disadvantage of the symmetric key is its disadvantaged process of distribution of the secret keys. Considering that the whole system is dependent on the secrecy of the key, this is a let off which consequently lead the system to be vulnerable. There are though some options one should consider.
One should foremost transport the key through secure channel manually; the media used may be trustworthy person or a concreted tunnel. The secret is then transported to the various nodes in place. There are however issues that tend to cause a disadvantage to the whole process, it takes a lot of time and is wastage of resources (Schneier, B., 2000). Moreover, it is hard to apply it in a distributed systems taking into consideration that each node is composed of a number of varied secret keys coherent to the varied elements involved. The keys are not transported over and over again.
Taking an assumption of the loyalty of the two elements, any breakage of the medium or the trust of the individual the key is then revoked. The revocation of the keys involves informing the other person of what has taken place; they then take another key and transport it to another individual who is much more trustworthy or just simply to another channel. If the situation occurs again, it is repeated again by transferring to another more trusted individual or otherwise another channel. A risky measure is that a third person may create a false revocation. Since there is no means of allowing access or denying access, the revocation is not encrypted. The third individual may as well easily access all the information. This system is quite open to individuals with bad intentions.
Secondly, away from the physical transit to the two elements, there is the hierarchy model where the two elements exchange secret data indirectly. When two persons establish a communication, the keys are quite numerous. Take an instance of John and Mary who establish a communication (Grover. D., 1990). They share a short session key Ks, it may gotten from either John or Mary the Ks is used to encrypt data. They similarly share another key called master key Kk whose life period is much lengthier and is located at the top most of the Ks and is used to encrypt the session key Ks. The transit process is done electronically. The protocol is explained as:
John: Ks
John- -Mary: EKk (Ks)
Mary: DKk (EKk (Ks))
Mary: Ks
The protocol displayed above is in ANSI (American National Standards Institute) standard X9.17 as a two tier structure. There is an advantage of applying the Kk to encrypt the Ks session key which is the minimized loss of secrecy. The disadvantage arises in the Kk master key which also is need for transit for a specific number of conversations. With a short period, the session key is reduced when compared to master key. When the master key losses its confidentiality issues arise like transit instances.
Thirdly, there is the introduction of third party who is trustworthy, otherwise Trusted Third Party (TTP) the structures involved are the key distribution and key translation centers. This third party is involved in the production of keys for each and every session which is quite unique with Peter who is the third person. The session key is encrypted with the shared key for every session. The same process is used to decrypt it. The procedure is explained better below:
Peter: Ks
Peter—John: EKa (Ks) || EKb (Ks)
John: DKa (EKa (Ks))
John: Ks
John—Mary: EKs (P) || EKb (Ks)
Mary: DKb (EKb (Ks))
Mary: DKs (EKs (P))
In this case, Peter sends to John a message where one is encrypted with Ka and the other one with Kb. When John receives the two encryptions, it may decide to format the second one to Mary so as to let Mary to be acquainted with the session Ks. The translation center key is contrastingly varied with the distribution center in that there is no production of session keys for the requests. The protocol is described below:
John: Ks
John—Peter; EKa (Ks)
Peter: DKa (EKa (Ks))
Peter: EKb (Ks)
Peter – John: EKb (Ks)
John – Peter; EKb (Ks)
Mary: DKb (EKb (Ks))
Mary: Ks
The key centers are flexible and quite efficient, the users require to change and place a master key without having to exchange the master key at each and every conversation. Revocation is however not upheld in the protocol but it minimizes the dangers through the managing of the secret key issue in KDC/KTC. A third person may still access information from this; consequently the lack of authentication is a serious disadvantage (Brooks, P., 2000). This can be corrected through the message authentication code as well as the hash function.
The revocation is done as follows:
Peter- -John: Eka (R || H(R))
John: Dka (Eka (R || H(R)))
John: H(R) ^
John: check if H(R) =H(R) ^
Message true, accept
Else
Discard and report.
John – – Peter: Eka (T|| H (T))
Peter: Dka (Eka (T|| H (T)))
Peter: H (T) ^
Peter: check if H (T) = H (T) ^
Message true, accept
Else
Discard and log
Peter: Ks
Peter — John: Eka (Ks) || EKb (Ks)
John: Dka (Eka (Ks))
John: Ks
John – -B: EKs (P) ||EKb (Ks)
Mary: DKb (EKb (Ks))
Mary: DKs (EKs (P))
The management of the problem between asymmetric and symmetric key; the public key has two keys one is private while the other one is public. As the key in asymmetric is modeled for public us, the confidentiality of the key in symmetric is not relevant for the significant other, asymmetric key system. Of key importance is the privacy of the data. The revocation of a key in public keying is considered in private keying. Since the private and the public keying are both together, when the secrecy of the private key is lost the whole pair of key is considered for replacement.
The public key system normally appears in varied models it is therefore of consequence that the revocation of the key are similarly different.
The public key is allocated through an announcement which is much better. This may however be a venue for forged announcements taking into public arena; moreover the announcements are trusted as there are no means of determining its correct nature (Engelfriet A, 1996). It however has an advantage in terms of digital signature function. This may however not plays a role when revoking a key as it is already compromised.
A measure of advancing the distribution is through the public directory. The directory takes all the public keys in the domains as opposed to the entities. The entities possess an entry through to the directory hence keeping at bay the chance of forging an announcement or identity. Any access to the directory is for the possibility of acquiring a public key.
There is a much better verification means otherwise called public key authority. This has some correlation to the directory; the only difference is that the authority key creates a verification means against the individual using it. This verification means is an added security measure through authentication by a digital signature. Take a situation where John wants to communicate to Mary; John will therefore have to send a request to the authority which would reply in addition to Mary’s public key as well as the time stamp which is encrypted through the secrecy key (Barkley, J., 1994). John will receive the message; he will then decrypt it using the authority’s public key which John shares with authority, Kau-. This procedure will ensure the reply is taken to its destined location from the authority not an individual. John will then send Mary a message using Mary’s public key so as to start the communication, Mary receives it and then sends to the authority a request for confirmation. The authority will send back a message including John’s public key as well as the time stamp which is encrypted by the authority’s public key Ka-. Mary will decrypt the received message using the public key shared between Mary and the authority. With all of them possessing the other parties public key a conversation may as well be created. The protocol is;
John- -Authority: request||Time1
Authority- – John: EKau-(Kb+||Time1)
John: DKau + (EKau-(Kb+||Time1))
John – -Mary: EKb+ (Ida||Time2)
Mary – -Authority: request|| Time3
Authority- – Mary: EKau – (Ka+||Time3)
Mary: DKau + (EKau – (Ka+||Time3))
Mary – – John: EKa+ (Time2||Time3)
John – -B: EKb+ (Time3)
The security analysis is related to the Kerberos authentication protocol, the hash function and the signature scheme. There are several threats that are most likely bound to attack the system from its normal operations;
Masquerade: this is normally when a user requires a certificate and disguises himself as another person. Kerberos is therefore used to detect such activities and stop them. There is the modification of data which helps to stop the alteration of the contents of a certificate. In situations like the alteration of the contents of the certificate in transit the integrity security protection means is used (Simonds. F and Ranade. J., 1996; Stallings. W., 1995). There is also the alteration of the certificates that are kept which is solved through the application of a storage means like the file system protection. In the event of an alteration of the security attributes before being packaged like the LDAP there is the use of means like Kerberos which is protected by LDAP.
In the event of a loss of confidentiality which means that a person who has the user’s key will automatically gain access. This renders it necessary to create a private key on the machine which similarly has to place secure from access by other persons. This is done so through the application of randomness in the user’s machine.
Statement of the resource requirements
The paper covered the key distribution as well as the revocation matters in the two cryptosystems symmetric and asymmetric. This is in attempt to issue or revoke the key(s) in a secure manner as well as efficient. There are several ways in which a person can revoke a key while similarly still others ways of distributing it. The points of consideration are how to optimize the chance of acquiring confidentiality, integrity of the message as well as the putting into practice the authentication so as determine the identities of the real users. The methods and processes as above put out clearly display this. To achieve this different protocols are used at the varied levels, the bets protocols are the ones that possess more features which is aimed at acquiring confidentiality, integrity with the spicing of authentication. No particular system can actually be termed to as 100% safe or otherwise perfect. The coming into being of new systems comes with far more advanced features, the systems do with time continue to advance and the future seems quite secure.
A web server is a necessary requirement in that it is used to offer access to various services. It may as well be a decision point and it still must much up to the security requirements of the system by offering access to only authorized persons like the administrators. The web server uses an end to end authentication mechanism which would similarly lead to an end to end authorization of the system (E-certify, 2004; Stallings, W., 2003). Any form of mismatch creates a hindrance from accessing the web server.
The distributed requirements of the distribution system has ultimately led to the advancement of the authorization and authentication means like the local login which is OS-specific an instance is the UNIX, the secure remote login which uses the SSH, Telnet and VPN, the secure transfer of information from the source to destination that uses https, scp and kftp. These are just but a few of the many others.
References
- Barkley, J. (1994) “Public Key Distribution”
http://csrc.nist.gov/publications/nistpubs/800-7/figoneca, 1994 (accessed 7th June 2011)
- Barkley, J., “Secret Key Distribution”
http://csrc.nist.gov/publications/nistpubs/800-7/node209.html, 1994 (accessed 7th June 2011)
- Brooks,P.,“Key Revocation”
http://www.ac.uk.pgp.net/pgpnet/secemail/q4/node9.html, 2000 (accessed 7th June 2011)
- E-certify, “Guide to Internet Security”
http://www.e-certify.com/library/cert_guide.html 2004 (accessed 7th June 2011)
- Engelfriet A (1996), “PGP FAQ–Revoking a key”
http://pgp.rasip.fer.hr/faqs/pgp/faq7.html, 1996 (accessed 7th June 2011)
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- A. J., Oorschot P. C. V., Vanstone S. A., “Handbook of Applied Cryptography” (revised reprint with updates, originally issued in 1965 ) CRC Press: London, 1997 pp31-40
- Rhee, M. Y., “Cryptograph and Secure Communications”, McGraw-Hill: Singapore, 1994 p461
- Schneier, B., “Secrets and Lies digital security in a networked world” John Wiley and Sons: New York, 2000 p215
- F and Ranade. J., “Network Security” McGraw-Hill: New York, 1996 p115
- W., “Network and Internetwork Security Principles and Practice” Prentice Hall: New Jersey, 1995 p87
- Stallings, W. “Cryptography and Network Security Principles and Practices” 3rd edition, Prentice Hall: New Jersey, 2003. Pp211-231, pp286-296
