computer science

Tiny Encryption Algorithm

Tiny Encryption Algorithm is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tiny Encryption Algorithm rather than just read about it. In short: In cryptography, the Tiny Encryption Algorithm (TEA) is a block cipher notable for its simplicity of description and implementation, typically a few lines of code. It was designed by David Wheeler and Roger Needham of the Cambridge Computer Laboratory; it was first presented at the Fast Software Encryption workshop in Leuven in 1994, and first published in the proceedings of that workshop.

Key takeaways

Tiny Encryption Algorithm belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tiny Encryption Algorithm to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tiny Encryption Algorithm from memory before moving on to harder problems.

Reference excerpt

In cryptography, the Tiny Encryption Algorithm (TEA) is a block cipher notable for its simplicity of description and implementation, typically a few lines of code. It was designed by David Wheeler and Roger Needham of the Cambridge Computer Laboratory; it was first presented at the Fast Software Encryption workshop in Leuven in 1994, and first published in the proceedings of that workshop. The cipher is not subject to any patents.

Properties TEA operates on two 32-bit unsigned integers (could be derived from a 64-bit data block) and uses a 128-bit key. It has a Feistel structure with a suggested 64 rounds, typically implemented in pairs termed cycles. It has an extremely simple key schedule, mixing all of the key material in exactly the same way for each cycle. Different multiples of a magic constant are used to prevent simple attacks based on the symmetry of the rounds. The magic constant, 2654435769 or 0x9E3779B9 is chosen to be ⌊232⁄𝜙⌋, where 𝜙 is the golden ratio (as a nothing-up-my-sleeve number). TEA has a few weaknesses. Most notably, it suffers from equivalent keys—each key is equivalent to three others, which means that the effective key size is only 126 bits. As a result, TEA is especially bad as a cryptographic hash function. This weakness led to a method for hacking Microsoft's Xbox game console, where the cipher was used as a hash function. TEA is also susceptible to a related-key attack which requires 223 chosen plaintexts under a related-key pair, with 232 time complexity. Because of these weaknesses, the XTEA cipher was designed.

Versions The first published version of TEA was supplemented by a second version that incorporated extensions to make it more secure. Block TEA (which was specified along with XTEA) operates on arbitrary-size blocks in place of the 64-bit blocks of the original. A third version (XXTEA), published in 1998, described further improvements for enhancing the security of the Block TEA algorithm.

Reference code Following is an adaptation of the reference encryption and decryption routines in C, released into the public domain by David Wheeler and Roger Needham:

Note that the reference implementation acts on multi-byte numeric values. The original paper does not specify how to derive the numbers it acts on from binary or other content.

See also RC4 – A stream cipher that, just like TEA, is designed to be very simple to implement. XTEA – First version of Block TEA's successor. XXTEA – Corrected Block TEA's successor. Treyfer – A simple and compact encryption algorithm with 64-bit key size and block size.

Notes

References Andem, Vikram Reddy (2003). "A Cryptanalysis of the Tiny Encryption Algorithm, Masters thesis" (PDF). Tuscaloosa: The University of Alabama. Hernández, Julio César; Isasi, Pedro; Ribagorda, Arturo (2002). "An application of genetic algorithms to the cryptoanalysis of one round TEA". Proceedings of the 2002 Symposium on Artificial Intelligence and Its Application. Hernández, Julio César; Sierra, José María; Isasi, Pedro; Ribargorda, Arturo (2003). "Finding efficient distinguishers for cryptographic mappings, with an application to the block cipher TEA". The 2003 Congress on Evolutionary Computation, 2003. CEC '03. Vol. 3. pp. 2189–2193. doi:10.1109/CEC.2003.1299943. hdl:10016/3944. ISBN 978-0-7803-7804-9. S2CID 62216777. Hernández, Julio César; Sierra, José María; Ribagorda, Arturo; Ramos, Benjamín; Mex-Perera, J. C. (2001). "Distinguishing TEA from a Random Permutation: Reduced Round Versions of TEA do Not Have the SAC or do Not Generate Random Numbers". Cryptography and Coding (PDF). Lecture Notes in Computer Science. Vol. 2260. pp. 374–377. doi:10.1007/3-540-45325-3_34. ISBN 978-3-540-43026-1. Archived from the original (PDF) on 26 April 2012. Moon, Dukjae; Hwang, Kyungdeok; Lee, Wonil; Lee, Sangjin; Lim, Jongin (2002). "Impossible Differential Cryptanalysis of Reduced Round XTEA and TEA". Fast Software Encryption (PDF). Lecture Notes in Computer Science. Vol. 2365. pp. 49–60. doi:10.1007/3-540-45661-9_4. ISBN 978-3-540-44009-3. Hong, Seokhie; Hong, Deukjo; Ko, Youngdai; Chang, Donghoon; Lee, Wonil; Lee, Sangjin (2004). "Differential Cryptanalysis of TEA and XTEA". Information Security and Cryptology - ICISC 2003. Lecture Notes in Computer Science. Vol. 2971. pp. 402–417. doi:10.1007/978-3-540-24691-6_30. ISBN 978-3-540-21376-5.

External links Test vectors for TEA JavaScript implementation of XXTEA with Base64 Archived 28 April 2006 at the Wayback Machine PHP implementation of XTEA (German language) JavaScript implementation of XXTEA JavaScript and PHP implementations of XTEA (Dutch text) AVR ASM implementation SEA Scalable Encryption Algorithm for Small Embedded Applications (Standaert, Piret, Gershenfeld, Quisquater - July 2005 UCL Belgium & MIT USA)

Illustrations

Worked examples

Example 1 — a first encounter with Tiny Encryption Algorithm

Start with the simplest possible case. Write down what Tiny Encryption Algorithm claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tiny Encryption Algorithm before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tiny Encryption Algorithm ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tiny Encryption Algorithm

In research: Tiny Encryption Algorithm appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tiny Encryption Algorithm in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tiny Encryption Algorithm is common in secondary-school and first-year university syllabi. It links to neighbouring topics Block ciphers, Broken block ciphers, Computer security in the United Kingdom, so understanding it makes those chapters shorter.
In everyday life: Look for Tiny Encryption Algorithm outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tiny Encryption Algorithm in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tiny Encryption Algorithm means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tiny Encryption Algorithm out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tiny Encryption Algorithm in simple terms?

Why does Tiny Encryption Algorithm matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tiny Encryption Algorithm?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tiny Encryption Algorithm.