Click here to close now.


IoT User Interface Authors: Elizabeth White, Pat Romanski, Gary Kaiser, Liz McMillan, Jnan Dash

Related Topics: Java IoT, Industrial IoT, Microservices Expo, IoT User Interface, Apache, Cloud Security

Java IoT: 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.

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.

@CloudExpo Stories
The buzz continues for cloud, data analytics and the Internet of Things (IoT) and their collective impact across all industries. But a new conversation is emerging - how do companies use industry disruption and technology enablers to lead in markets undergoing change, uncertainty and ambiguity? Organizations of all sizes need to evolve and transform, often under massive pressure, as industry lines blur and merge and traditional business models are assaulted and turned upside down. In this new da...
Containers are revolutionizing the way we deploy and maintain our infrastructures, but monitoring and troubleshooting in a containerized environment can still be painful and impractical. Understanding even basic resource usage is difficult - let alone tracking network connections or malicious activity. In his session at DevOps Summit, Gianluca Borello, Sr. Software Engineer at Sysdig, will cover the current state of the art for container monitoring and visibility, including pros / cons and li...
The Internet of Things (IoT) is growing rapidly by extending current technologies, products and networks. By 2020, Cisco estimates there will be 50 billion connected devices. Gartner has forecast revenues of over $300 billion, just to IoT suppliers. Now is the time to figure out how you’ll make money – not just create innovative products. With hundreds of new products and companies jumping into the IoT fray every month, there’s no shortage of innovation. Despite this, McKinsey/VisionMobile data...
As-a-service models offer huge opportunities, but also complicate security. It may seem that the easiest way to migrate to a new architectural model is to let others, experts in their field, do the work. This has given rise to many as-a-service models throughout the industry and across the entire technology stack, from software to infrastructure. While this has unlocked huge opportunities to accelerate the deployment of new capabilities or increase economic efficiencies within an organization, i...
There are so many tools and techniques for data analytics that even for a data scientist the choices, possible systems, and even the types of data can be daunting. In his session at @ThingsExpo, Chris Harrold, Global CTO for Big Data Solutions for EMC Corporation, will show how to perform a simple, but meaningful analysis of social sentiment data using freely available tools that take only minutes to download and install. Participants will get the download information, scripts, and complete en...
Containers are changing the security landscape for software development and deployment. As with any security solutions, security approaches that work for developers, operations personnel and security professionals is a requirement. In his session at @DevOpsSummit, Kevin Gilpin, CTO and Co-Founder of Conjur, will discuss various security considerations for container-based infrastructure and related DevOps workflows.
Manufacturing has widely adopted standardized and automated processes to create designs, build them, and maintain them through their life cycle. However, many modern manufacturing systems go beyond mechanized workflows to introduce empowered workers, flexible collaboration, and rapid iteration. Such behaviors also characterize open source software development and are at the heart of DevOps culture, processes, and tooling.
Between the compelling mockups and specs produced by analysts, and resulting applications built by developers, there exists a gulf where projects fail, costs spiral, and applications disappoint. Methodologies like Agile attempt to address this with intensified communication, with partial success but many limitations. In his session at DevOps Summit, Charles Kendrick, CTO and Chief Architect at Isomorphic Software, will present a revolutionary model enabled by new technologies. Learn how busine...
There are many considerations when moving applications from on-premise to cloud. It is critical to understand the benefits and also challenges of this migration. A successful migration will result in lower Total Cost of Ownership, yet offer the same or higher level of robustness. Migration to cloud shifts computing resources from your data center, which can yield significant advantages provided that the cloud vendor an offer enterprise-grade quality for your application.
IT data is typically silo'd by the various tools in place. Unifying all the log, metric and event data in one analytics platform stops finger pointing and provides the end-to-end correlation. Logs, metrics and custom event data can be joined to tell the holistic story of your software and operations. For example, users can correlate code deploys to system performance to application error codes.
Internet of Things (IoT) will be a hybrid ecosystem of diverse devices and sensors collaborating with operational and enterprise systems to create the next big application. In their session at @ThingsExpo, Bramh Gupta, founder and CEO of, and Fred Yatzeck, principal architect leading product development at, discussed how choosing the right middleware and integration strategy from the get-go will enable IoT solution developers to adapt and grow with the industry, while at th...
The web app is agile. The REST API is agile. The testing and planning are agile. But alas, data infrastructures certainly are not. Once an application matures, changing the shape or indexing scheme of data often forces at best a top down planning exercise and at worst includes schema changes that force downtime. The time has come for a new approach that fundamentally advances the agility of distributed data infrastructures. Come learn about a new solution to the problems faced by software organ...
The last decade was about virtual machines, but the next one is about containers. Containers enable a service to run on any host at any time. Traditional tools are starting to show cracks because they were not designed for this level of application portability. Now is the time to look at new ways to deploy and manage applications at scale. In his session at @DevOpsSummit, Brian “Redbeard” Harrington, a principal architect at CoreOS, will examine how CoreOS helps teams run in production. Attende...
“All our customers are looking at the cloud ecosystem as an important part of their overall product strategy. Some see it evolve as a multi-cloud / hybrid cloud strategy, while others are embracing all forms of cloud offerings like PaaS, IaaS and SaaS in their solutions,” noted Suhas Joshi, Vice President – Technology, at Harbinger Group, in this exclusive Q&A with Cloud Expo Conference Chair Roger Strukhoff.
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...
Cloud computing delivers on-demand resources that provide businesses with flexibility and cost-savings. The challenge in moving workloads to the cloud has been the cost and complexity of ensuring the initial and ongoing security and regulatory (PCI, HIPAA, FFIEC) compliance across private and public clouds. Manual security compliance is slow, prone to human error, and represents over 50% of the cost of managing cloud applications. Determining how to automate cloud security compliance is critical...
SYS-CON Events announced today that VividCortex, the monitoring solution for the modern data system, will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. The database is the heart of most applications, but it’s also the part that’s hardest to scale, monitor, and optimize even as it’s growing 50% year over year. VividCortex is the first unified suite of database monitoring tools specifically desi...
Saviynt Inc. has announced the availability of the next release of Saviynt for AWS. The comprehensive security and compliance solution provides a Command-and-Control center to gain visibility into risks in AWS, enforce real-time protection of critical workloads as well as data and automate access life-cycle governance. The solution enables AWS customers to meet their compliance mandates such as ITAR, SOX, PCI, etc. by including an extensive risk and controls library to detect known threats and b...
You have your devices and your data, but what about the rest of your Internet of Things story? Two popular classes of technologies that nicely handle the Big Data analytics for Internet of Things are Apache Hadoop and NoSQL. Hadoop is designed for parallelizing analytical work across many servers and is ideal for the massive data volumes you create with IoT devices. NoSQL databases such as Apache HBase are ideal for storing and retrieving IoT data as “time series data.”
Clearly the way forward is to move to cloud be it bare metal, VMs or containers. One aspect of the current public clouds that is slowing this cloud migration is cloud lock-in. Every cloud vendor is trying to make it very difficult to move out once a customer has chosen their cloud. In his session at 17th Cloud Expo, Naveen Nimmu, CEO of Clouber, Inc., will advocate that making the inter-cloud migration as simple as changing airlines would help the entire industry to quickly adopt the cloud wit...