Click here to close now.

Welcome!

XML Authors: Elizabeth White, Carmen Gonzalez, Pat Romanski, AppDynamics Blog, Yeshim Deniz

Related Topics: Java, XML, Microservices Journal, AJAX & REA, Apache, Security

Java: Article

Designing a Java Cryptography Header

Encrypt personal files, exchange confidential messages and authenticate the sender

Designing and implementing a hybrid encryption application is a big challenge but without a supporting infrastructure it's almost impossible. There are open source libraries that allow you to encrypt a file but only provide the translation technique. After the information has been encrypted, how do you know what algorithm was used, who you encrypted it, what version did you used, etc. In order to decrypt the protected message or file, a well-defined cryptographic header provides all the information required. This also applies if the encrypted data is digitally signed and the recipient wants to validate the signature.

This article will address one of the critical components of a support infrastructure by providing a design of a cryptographic header used to precede encrypted and/or digitally signed messages and files. The header is used within an application known as DocuArmor that was written using Java and the Cryptography library from the BouncyCastle organization and designed by Logical Answers Inc. The header will store information used when encrypting and/or digitally signing a message or file and allow the recipient to decrypt the information and/or verify the digital signature. With a properly designed header, a person can encrypt their personal files as well as exchange confidential messages and authenticate the sender.

Hybrid Encryption
In order to encrypt personal files and exchange protected data, we use a hybrid technique with two types of encryption, symmetric and asymmetric.

Symmetric encryption uses a single key to hide the message and reveal the message. There are several symmetric algorithms available such as AES (the Advanced Encryption Standard) but the important thing to remember is that the file can be encrypted and decrypted using the same key. An example is the Caesar cipher that shifts the letters of the alphabet by a specific number. If the shift is 2 (single key) then we get the following translation; a=c, b=d, c=e, ..., z=b.

Asymmetric encryption uses a pair of keys (public, private) to hide and reveal the message and the RSA algorithm is most commonly used. The RSA algorithm was credited in 1977 to Ronald Rivest, Adi Shamir, and Leonard Adleman. Sometimes referred to as Public Key Infrastructure (PKI), the pubic key is used to encrypt data and the private key is used to decrypt data.

Figure 1: Public and Private Key Functions

The hybrid technique uses the symmetric key to encrypt a file. The asymmetric public key is used to encrypt the symmetric key and is placed in the header. When the recipient receives an encrypted file, the encrypted symmetric key is extracted from the header. The encrypted symmetric key is decrypted using the private key. The file is decrypted using the symmetric key.

The same pair of keys can be used with digital signatures. The private key is used to generate a digital signature from a file and inserted into the header. The public key is used to verify the authenticity of the signature.

When two people want to exchange encrypted files, they each generate a pair of asymmetric keys and exchange a copy of their public keys. By using the other person's public key, they can encrypt a file, storing the cryptographic information in the header and then e-mail it to the recipient. The recipient will use the header to extract a symmetric key with their private key and decrypt the accompanying file. If a digital signature is included, the recipient can authenticate the sender.

Figure 2: Exchange of Encrypted Files

Cryptographic Header
When a file is encrypted, digitally signed or both, a Cryptographic header is placed in front of the resulting file and has the following structure. The structure consists of two sections, the header and the encrypted/plain file contents.

Figure 3: Encrypted File Structure

The header structure contains information required to reverse the encryption process and decrypt the contents of the file or verify the digital signature. The header contains the total length, an ID, version, and two sections containing encryption and digital signature information. Using Java, you can write out the contents of header within a byte stream as well as read it back in.

Figure 4: Cryptographic Header Structure

  • Total Len: Contains the total length of the header (stored as a 4 byte integer)
  • Header ID: Contains the string "LAHEADER" to identify the file (16 bytes)
  • Header Version: Structural version of the header (stored as a 4 byte integer)
  • Encryption Information: Holds the algorithm, mode, encrypted symmetric key, etc.
  • Digital Signature Information: Holds digital signature

Encryption Information
The Encryption Information structure contains information that was used to encrypt the contents of the file and later decrypt the file. The symmetric key and initialization vector is encrypted with the recipient's asymmetric public key. The recipient could be the owner if you are encrypting a file for yourself or another user you want to send confidential information to.

An additional field has been allocated to allow the encryption of the symmetric key with another set of asymmetric keys. For example, if owner A is sending an encrypted file to another person B, the symmetric key can be encrypted with B's public key as well as A's public key so that either person can decrypt the file.

Alternatively, an employee can encrypt a file with their public key and a corporation could insert an encrypted symmetric key into the header using their asymmetric keys. The corporation's asymmetric keys can be a Certifying Authority (CA), which can be used to issue employee keys.

Figure 5: Encryption Information Structure

  • Encrypt Flag: (Y/N - 2 bytes) specifies whether the file is encrypted.
  • Decrypt ID Length: (integer - 4 bytes) length in chars(bytes) of the Key ID.
  • Decrypt ID: (size varies) an identifier of the RSA keys used in the encryption/decryption process. It is the alias associated to the asymmetric encryption keys (e.g., JaneDoe_12ff).
  • Other Decrypt ID Length: (integer - 4 bytes) length in chars(bytes) of the Key ID.
  • Other Decrypt ID: (size varies) an identifier of the RSA keys used in the encryption/decryption process. It can be the alias or the common name (e.g., JaneDoe_12ff or Logical Answers CA).
  • Symmetric Key Algorithm: (integer - 4 bytes) specifies the symmetric key algorithm used to encrypt the file. The default value is 1=AES.
  • Symmetric Key Mode: (integer - 4 bytes) specifies the symmetric key block cipher mode used to enhance confidentiality. The default value is 5=Segmented Integer Counter mode (CTR).
  • Symmetric Key Padding: (integer - 4 bytes) specifies the type of padding for block cipher. The default value is 1=No Padding
  • Wrapped Symmetric Key Length: (integer - 4 bytes)
  • Wrapped Symmetric Key: (size varies) symmetric key used to encrypt/decrypt the file and encrypted with the asymmetric key.
  • Initialization Vector Length: (integer - 4 bytes)
  • Initialization Vector: (byte[] - size varies) vector used with the symmetric encryption process.
  • Other Wrapped Symmetric Key Length: (integer - 4 bytes)
  • Other Wrapped Symmetric Key: (size varies) symmetric key used to encrypt/decrypt the file and encrypted with another person's asymmetric key.
  • Other Initialization Vector Length: (integer - 4 bytes)
  • Other Initialization Vector: (byte[] - size varies) vector used with the symmetric encryption process.

Digital Signature Information
The Digital Signature Information structure contains information used to add or verify a digital signature generated from the contents of the file. The digital signature is generated with the owner's private key using a specific algorithm and then inserted into the header. When the recipient receives the signed file, they can use the signer's public key to validate its authenticity. If the signature is authenticated, it implies the file has not been altered and the holder of the private key generated the signature.

Figure 6: Digital Signature Information Structure

  • Signed Flag: (Y/N - 2 bytes) specifies whether the file contains a digital signature
  • Signature Algorithm: (integer - 4 bytes) specifies the algorithm used to generate the digital signature. The default value is 12= SHA512WithRSAEncryption
  • Verify Signature Cert Name Length: (integer - 4 bytes) length in chars(bytes) of the filename of the certificate used to verify a digital signature
  • Verify Signature Cert Name: (size varies) filename of the certificate holding the RSA public key used to verify the digital signature of a file (e.g., JaneDoe_fa39.cer).
  • Signature Date/Time: (long - 8 bytes) date the digital signature was generated.
  • Signature Length: (integer - 4 bytes)
  • Signature: (size varies) holds digital signature generated with RSA private key and signature engine

File Naming Conventions
The Cryptographic header holds information that designates which keys were used to encrypt a file but it's not physically accessible without reading it in first. With proper naming conventions, you can determine who the intended recipient is for encrypted files - whether it is for yourself or a colleague. When you generate your pair of asymmetric encryption keys using Java, store them in a file called a key store. The key store holds a pair of asymmetric keys as an entry with a unique alias. The alias typically consists of the initial of your first name and your last name. To make it more unique, you can extract 4 hex digits from your public key and append an underline and the hex digits to the alias. For example, if the person's name was Jane Smith, then the resulting unique alias would be jsmith_ad5e. A certificate holds a person's public key and the alias would be used in the filename, as jsmith_ad5e.cer. Similarly, the key store holding the pair of asymmetric keys would be saved as, jsmith_ad5e.jks.

Following the unique alias analogy, Jane Smith could encrypt files for herself and the file name would be appended with her alias and an appropriate file extension. For example, if Jane encrypted a personal file, myTaxes.txt, then the result would be myTaxes.txt.jsmith_ad5e.aes. If Jane wanted to send her colleague Dick an encrypted document, she would use Dick's certificate to encrypt it. If Dick's certificate is djones_9fa2, Jane could encrypt the file, comments.doc, for Dick and the resulting file would be comments.doc.djones_9fa2.aes. When Dick receives the file, he knows it is for him by recognizing his alias on the file name.

The unique alias is stored within the header. This reinforces the importance of having a well-defined Cryptographic header for implementing encryption within your applications.

Benefits
A well-defined cryptographic header stores the information required to encrypt, decrypt and digitally sign a file. Along with facilitating the implementation of standard cryptographic functions, the header also provides the following benefits:

  • The header allows for the protection of personal files as well as the exchange of confidential data.
  • Using the stored digital signature, the recipient can determine if the sender is valid and whether file has been altered.
  • The header allows either the sender or recipient to decrypt the encrypted file since both would encrypt the symmetric key with their public key.
  • Using the concept of a Certifying Authority pair of asymmetric keys, a corporation, group, or family could issue pairs of asymmetric keys to their employees or members and decipher files encrypted by them in case of emergencies.
  • The header allows for using different combinations of symmetric algorithms, modes, padding and key sizes to be used to encrypt information.
  • The header version allows for enhancements to be added to the structure for implementing new functions and still support older versions.

References and Other Technical Notes
Software requirements:

Recommended Reading:

  • "Beginning Cryptography with Java" by David Hook.
  • "The Code Book" by Simon Singh

More Stories By James H. Wong

James H. Wong has been involved in the technology field for over 30 years and has dual MS degrees in mathematics and computer science from the University of Michigan. He worked for IBM for almost 10 years designing and implementing software. Founding Logical Answers Corp in 1992, he has provided technical consulting/programming services to clients, providing their business with a competitive edge. With his partner they offer a Java developed suite of “Secure Applications” that protect client’s data using the standard RSA (asymmetric) and AES (symmetric) encryption algorithms.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
The Internet of Things will put IT to its ultimate test by creating infinite new opportunities to digitize products and services, generate and analyze new data to improve customer satisfaction, and discover new ways to gain a competitive advantage across nearly every industry. In order to help corporate business units to capitalize on the rapidly evolving IoT opportunities, IT must stand up to a new set of challenges. In his session at @ThingsExpo, Jeff Kaplan, Managing Director of THINKstrategies, will examine why IT must finally fulfill its role in support of its SBUs or face a new round of...
Can call centers hang up the phones for good? Intuitive Solutions did. WebRTC enabled this contact center provider to eliminate antiquated telephony and desktop phone infrastructure with a pure web-based solution, allowing them to expand beyond brick-and-mortar confines to a home-based agent model. It also ensured scalability and better service for customers, including MUY! Companies, one of the country's largest franchise restaurant companies with 232 Pizza Hut locations. This is one example of WebRTC adoption today, but the potential is limitless when powered by IoT.
One of the biggest challenges when developing connected devices is identifying user value and delivering it through successful user experiences. In his session at Internet of @ThingsExpo, Mike Kuniavsky, Principal Scientist, Innovation Services at PARC, described an IoT-specific approach to user experience design that combines approaches from interaction design, industrial design and service design to create experiences that go beyond simple connected gadgets to create lasting, multi-device experiences grounded in people's real needs and desires.
The 4th International Internet of @ThingsExpo, co-located with the 17th International Cloud Expo - to be held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA - announces that its Call for Papers is open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than 20 years ago.
Wearable devices have come of age. The primary applications of wearables so far have been "the Quantified Self" or the tracking of one's fitness and health status. We propose the evolution of wearables into social and emotional communication devices. Our BE(tm) sensor uses light to visualize the skin conductance response. Our sensors are very inexpensive and can be massively distributed to audiences or groups of any size, in order to gauge reactions to performances, video, or any kind of presentation. In her session at @ThingsExpo, Jocelyn Scheirer, CEO & Founder of Bionolux, will discuss ho...
The true value of the Internet of Things (IoT) lies not just in the data, but through the services that protect the data, perform the analysis and present findings in a usable way. With many IoT elements rooted in traditional IT components, Big Data and IoT isn’t just a play for enterprise. In fact, the IoT presents SMBs with the prospect of launching entirely new activities and exploring innovative areas. CompTIA research identifies several areas where IoT is expected to have the greatest impact.
Every day we read jaw-dropping stats on the explosion of data. We allocate significant resources to harness and better understand it. We build businesses around it. But we’ve only just begun. For big payoffs in Big Data, CIOs are turning to cognitive computing. Cognitive computing’s ability to securely extract insights, understand natural language, and get smarter each time it’s used is the next, logical step for Big Data.
The Internet of Things will greatly expand the opportunities for data collection and new business models driven off of that data. In her session at @ThingsExpo, Esmeralda Swartz, CMO of MetraTech, discussed how for this to be effective you not only need to have infrastructure and operational models capable of utilizing this new phenomenon, but increasingly service providers will need to convince a skeptical public to participate. Get ready to show them the money!
SYS-CON Events announced today that MetraTech, now part of Ericsson, has been named “Silver Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. Ericsson is the driving force behind the Networked Society- a world leader in communications infrastructure, software and services. Some 40% of the world’s mobile traffic runs through networks Ericsson has supplied, serving more than 2.5 billion subscribers.
The 17th International Cloud Expo has announced that its Call for Papers is open. 17th International Cloud Expo, to be held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, APM, APIs, Microservices, Security, Big Data, Internet of Things, DevOps and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit your speaking proposal today!
17th Cloud Expo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterprises are using some form of XaaS – software, platform, and infrastructure as a service.
The Internet of Things is not new. Historically, smart businesses have used its basic concept of leveraging data to drive better decision making and have capitalized on those insights to realize additional revenue opportunities. So, what has changed to make the Internet of Things one of the hottest topics in tech? In his session at @ThingsExpo, Chris Gray, Director, Embedded and Internet of Things, discussed the underlying factors that are driving the economics of intelligent systems. Discover how hardware commoditization, the ubiquitous nature of connectivity, and the emergence of Big Data a...
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo in Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal an...
All major researchers estimate there will be tens of billions devices - computers, smartphones, tablets, and sensors - connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades. With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo, June 9-11, 2015, at the Javits Center in New York City. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be
Container frameworks, such as Docker, provide a variety of benefits, including density of deployment across infrastructure, convenience for application developers to push updates with low operational hand-holding, and a fairly well-defined deployment workflow that can be orchestrated. Container frameworks also enable a DevOps approach to application development by cleanly separating concerns between operations and development teams. But running multi-container, multi-server apps with containers is very hard. You have to learn five new and different technologies and best practices (libswarm, sy...
SYS-CON Events announced today that DragonGlass, an enterprise search platform, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. After eleven years of designing and building custom applications, OpenCrowd has launched DragonGlass, a cloud-based platform that enables the development of search-based applications. These are a new breed of applications that utilize a search index as their backbone for data retrieval. They can easily adapt to new data sets and provide access to both structured and unstruc...
As the Internet of Things unfolds, mobile and wearable devices are blurring the line between physical and digital, integrating ever more closely with our interests, our routines, our daily lives. Contextual computing and smart, sensor-equipped spaces bring the potential to walk through a world that recognizes us and responds accordingly. We become continuous transmitters and receivers of data. In his session at @ThingsExpo, Andrew Bolwell, Director of Innovation for HP's Printing and Personal Systems Group, discussed how key attributes of mobile technology – touch input, sensors, social, and ...
WebRTC defines no default signaling protocol, causing fragmentation between WebRTC silos. SIP and XMPP provide possibilities, but come with considerable complexity and are not designed for use in a web environment. In his session at @ThingsExpo, Matthew Hodgson, technical co-founder of the Matrix.org, discussed how Matrix is a new non-profit Open Source Project that defines both a new HTTP-based standard for VoIP & IM signaling and provides reference implementations.
SYS-CON Events announced today that the "First Containers & Microservices Conference" will take place June 9-11, 2015, at the Javits Center in New York City. The “Second Containers & Microservices Conference” will take place November 3-5, 2015, at Santa Clara Convention Center, Santa Clara, CA. Containers and microservices have become topics of intense interest throughout the cloud developer and enterprise IT communities.
Buzzword alert: Microservices and IoT at a DevOps conference? What could possibly go wrong? In this Power Panel at DevOps Summit, moderated by Jason Bloomberg, the leading expert on architecting agility for the enterprise and president of Intellyx, panelists will peel away the buzz and discuss the important architectural principles behind implementing IoT solutions for the enterprise. As remote IoT devices and sensors become increasingly intelligent, they become part of our distributed cloud environment, and we must architect and code accordingly. At the very least, you'll have no problem fil...