Tiny Encryption Algorithm (TEA) was a fast and simple block cipher designed by Roger Needham and David Wheeler. This cipher uses simple 32-bit operations such XORs, Additions, Subtractions and Shifts. Initially, those instructions were not applicable directyly to PIC18F4550. However those 32-bit instructions are availabe under emulation. Here is an example of Tiny Encryption Algorithm (TEA) implementation on PIC18F4550, hopefully you enjoy it 
. The program are available under GNU Public License v3.0. Please feel free to use it without any warranty implied. Leave your comment below, so i can hear your voice. Happy coding 
.
Below is test the result of TEA test vector and it has satisfactory results, the same as specification 
,
Test Vector Result:
Plain Text : 0×0123456789abcdef
Cipher Key : 0×00112233445566778899aabbccddeeff
Cipher Text : 0×126c6b92c0653a3e
Plain Text
Note : Cipher Key is marked red
Cipher Text
Note : Cipher Key is marked red
RELATED STUFF
Download:
Source Code | v1.0
PIC18F4550 Datasheet
TEA Specification
TEA PIC18F4550 Documentation
MPLAB v8.10
Reference:
Tiny Encryption Algorithm
Roger Needham
David Wheeler
Bonjour
j’ai besoin d’aide,afin de trouver une solution et de comprendre ce cryptage.
Y a-t-il un moyen de décrypter ces données ?
J’ai une carte électronique qui crypte les données avant de les expédies au PC et un logiciel qui me sert a réceptionné les donnes.
Mais je les envoies a un ami par mail et lui peut les décryptées, mais c’est lui qui
A c réer ces programmes.
Mais j’ai le texte en claire et je peux le créer mais pour la sauvegarde c’est le pic16f876
Qui crypte avant de les ecrires dans la mémoire externe.
cinqtrois@yahoo.fr
Merci pour votre aide
TEXTE CLAIRE 9876543210 ET HORLOGE A ZERO (00:00) ET DATE 1 JANVIER 2000
—————————–TEXTE CODER———————————
ªõñ-W_ªõQR+¸æä++dÒü¨ìë¸æöÒ ÌîúÄÔòîίäÀÒ𶱩îÎÚø¾»¿ôÖÄà ¡¿èÐÀ½êÈÜþ¸¹§èÈØú¼¹
¡îÈÜ侧¿òÐÎ⦧¿òÜÀè®U³&4ꬫM&4TSE,>X]E*8BE_
õQC*8^]A(:BEA2VUK.<^[C4$@A[.F[C4″DnxJnzXLh|XJC[0″ RIJ> R0pXJAJ<~^JNn R<$RN_
õQn RMUlzXOYBn.ROJnzDG_0 DC[2″JC[0$þ
—————————–SANS LES CARACTERES—————————
d U 4 M 4 T S E X E 8 B E C
8 A B E A 2 V U K C 4 A J O
W F C 4 D n x J n z X L h X
J C 0 0 R I J R 0 p X J A J
J N n R R N n R M U l z X O
Y B n R O J n z D G 0 D C 2
J C 0
——————————CHIFFRE—————————————
4 4 8 8 2 4 4 0 0 0 2 0
4=4 fois 8=2 fois
2=2 fois 0=4 fois
manque le: 1 3 5 6 7 9
——————————MINUSCULE————————————-
d n x n z h p n n l z n n z
d=1 fois n=6 fois x=1 fois
z=2 fois h=1 fois p=1 fois
l=1 fois
d n x z h p l
——————————MAJUSCULE————————————-
U M T S E X E B E C A B E A V
U K C A J O W F C D J X L X J
C R I J R X J A J J N R R N R
M U X O Y B R O J D G D C J C
U=3 fois M=2 fois T=1 fois S=1 fois E=4 fois X=5 fois
B=2 fois C=6 fois A=4 fois V=1 fois K=1 fois J=9 fois
O=2 fois W=1 fois F=1 fois D=3 fois L=1 fois R=5 fois
I=1 fois N=2 fois Y=1 fois G=1 fois
U M T S E X B C A V K J O W F D L R I N Y G
manque le: H P Q Z
—————————————————————————-
F5 51 00 80 52 95 2B 01 B8 E6 E4 2B 2B 64 D2 FC
8A A8 EC EB 8D B8 E6 F6 D2 9A 9D 85 CC EE FA C4
82 87 9B D4 F2 EE CE 8E 8B AF E4 C0 D2 F0 B6 B1
A9 EE CE DA F8 BE BB BF F4 D6 C4 E0 A0 A1 BF E8
D0 C0 EE AA A1 BD EA C8 DC FE B8 B9 A7 E8 C8 D8
FA BC B9 A1 EE C8 DC E4 BE A7 BF F2 D0 CE E2 A6
A7 BF F2 DC C0 E8 AE 55 B3 06 26 34 EA AC AB 4D
06 26 34 12 54 53 45 0C 2C 3E 1C 58 5D 45 0E 2A
38 04 42 45 80 5F
F5 51 01 80 43 16 2A 38 18 5E 5D 41 0C 28 3A 04
42 45 41 0A 20 32 16 56 55 4B 02 2E 3C 18 5E 5B
43 16 34 24 06 40 41 5B 10 3C 2E 0E 4A 4F 57 1C
3E 2E 02 46 5B 43 0A 34 22 0C 44 13 03 18 6E 78
0A 18 19 01 4A 6E 7A 58 1E 1F 01 4C 68 7C 58 4A
43 5B 12 30 22 06 5C 11 05 10 30 20 52 1E 49 05
4A 3E 20 52 1E 1D 07 10 30 70 58 4A 41 0B 4A 3C
7E 5E 4A 13 07 4E 6E 20 52 18 1F 07 1E 3C 24 52
18 1D 07 4E 0F 5F
F5 51 02 80 6E 20 52 1A 4D 55 12 6C 7A 58 1E 4F
59 42 6E 2E 52 1E 4F 0B 4A 6E 7A 0C 44 47 5F 10
30 20 02 44 43 5B 16 32 22 06 4A 43 5B 10 30 24
FE 47 5F
——————————————————————————-
Comment by PAUL — 22 February 2009 @ 8:27 pm
@paul : sorry to say dude, i have no capability to answer your question. your question seems to be solved with cryptanalysis skill, which i have not learned yet. again, sorry to say, your questions about “what type of encryption” and “how to decrypt” with respect to data you supplied is hard to answer.
However, if you supply me the complete specification of those cipher algorithm. i’m probably able to help you.
Thank you for visiting my blog. Good Luck
Comment by edipermadi — 23 February 2009 @ 9:35 am
Hello
This crypt has an electronic card-based and pic16f876 eeprom
24lc512.
The microcontroller saves 40 bytes of data and only the maximum
Numeric characters. Of 0123456789.
But before it encrypts the data and that I am reading with a terminal
The data are received crypts.
And I do not know how?
I read your messages you have experience compared moi.Vous talk about
Encryption microchip microcontroller.
TEA Encryption on MEL PICBASIC Forum
Here are links where you can download programs and screenshots.
Thank you for your help
http://dl.free.fr/pZZOtQt48
http://dl.free.fr/akZIJYI3k
Comment by PAUL — 24 February 2009 @ 5:20 pm
Bonjour
Merci de ta reponse mais je n’y connais rien et je cherche sur divers forums et
Personne ne peut me dire de quel cryptage ?
.
Ce texte crypté vient d’une carte électronique à base de pic16f876 et une eeprom
24lc512.
Le microcontrôleur sauvegardes de données de 40 octets maximum et seulement des
caractères numériques. 0123456789.
Mais avant il crypte ses données et des que je fais une relecture avec un terminal
les données sont reçus cryptes.
Comme le cryptage est brouillé par des caractères, chiffres, lettres d’alphabet
J’ai fait des testes avec l’heure a 00 :00 et la date 01/01 /2000 et j’ai fait une
sauvegarde a chaque minute, sauvegarde a 00:00, 00:01,
00:02 , 00:03, 00:04, 00:05, 00:06, 00:07, 00:08, 00:09, 00:10
A fin de comprendre comment le cryptage se fait, donc + 1 a chaque fois
Et même avec très peu de chiffres ce n’est pas évident.
Et je ne sais pas comment faire ?
Voici des liens ou vous pouvez télécharger les programmes et les captures d’écran.
Merci de votre aide
http://dl.free.fr/pZZOtQt48
http://dl.free.fr/akZIJYI3k
Comment by paul — 25 February 2009 @ 6:42 pm
Hello
Thank you for your answer but I do not know anything and I’m looking on various forums and
Nobody can tell me what encryption?
.
This text comes from an encrypted electronic card-based and pic16f876 eeprom
24lc512.
The microcontroller saves 40 bytes of data and only the maximum
numeric characters. 0123456789.
But before it encrypts the data and that I am reading with a terminal
the data are received crypts.
As encryption is obscured by characters, figures, letters of alphabet
I did tests with a time 00: 00 and the date 01/01 / 2000 and I made a
every minute backup, backup 00:00, 00:01,
00:02, 00:03, 00:04, 00:05, 00:06, 00:07, 00:08, 00:09, 00:10
In order to understand how the encryption is done, so + 1 each time
Even with very little data that is not obvious.
And I do not know how?
Here are links where you can download programs and screenshots.
Thank you for your help
http://dl.free.fr/pZZOtQt48
http://dl.free.fr/akZIJYI3k
Comment by paul — 25 February 2009 @ 6:44 pm
@paul:
OK’ i got your file. let me try first.
Comment by edipermadi — 26 February 2009 @ 9:34 am
Hello
You have my email address and I let you think
Comment by paul — 26 February 2009 @ 4:48 pm
Hello
I do not think encryption but data compression.
On that website he talks about compression eeprom 512k and it’s like
for my problem
Good courage
Thank you
http://www.picbasic.co.uk/forum/showthread.php?t=6521&highlight=compression
http://www.picbasic.co.uk/forum/showthread.php?t=2813&highlight=compression
Comment by PAUL — 1 March 2009 @ 8:00 pm
@paul : sounds unfamiliar to me. please try to ask other people which master compression.
Comment by edipermadi — 5 March 2009 @ 10:58 am
Hello
I do not know, I guess it’s quality of compression, because I do not know
Not how it is encrypted.
Encryption reduces the bytes and is the opposite.
Do you know the encryption microcontroller and data from the eeprom 512k.
Thank you for your help
Comment by paul — 5 March 2009 @ 5:18 pm
edipermadi:
I have a question, i have written vhdl code for TEA and verified that it works by using your results…however, i tried varying the number of rounds say for example to 40,64 or any such value and it doesn’t work anymore! do i need to change the delta value or something, because according to the author, TEA has *variable* rounds..? please help!!! thanks
Comment by Shirley G — 10 March 2009 @ 10:56 am
@ Shirley G :
Hmmm… let me try first…
Or you can try to emulate your code in another easy laguage such as PHP. It will help you to debug your VHDL code.
Comment by edipermadi — 10 March 2009 @ 6:06 pm
Hello
I too do not know how and I do not understand what
you ask me (the delta change).
thank you
Comment by paul — 10 March 2009 @ 6:01 pm
@edipermadi:
I don’t know php, and I am trying to implement this design on an FPGA (hence i need it in vhdl) or C..thank you for responding..please let me know if you get variable rounds to work
@paul:
I meant, does the delta value need to be changed (from the constant value 0×9e3779b9) in accordance with the number of rounds..This is just a guess..because if i just change number of rounds to say 40 or something like a random number if i encrypt and decrypt it using that random value, i do not get the original plaintext…it works perfectly only if the number of rounds is 32..i hope this explains my question more clearly….
Comment by Shirley G — 11 March 2009 @ 12:27 am
Shirley G :
I think the problem comes from the delta constant. The delta constant in your encryption and decryption routine were fixed to 32 rounds.
For Example (Normal Situation 32 rounds)
In Encryption : delta = 0×9e3779b9
In decryption : delta = (0×9e3779b9 x 32)% 0xffffffff = 0xc6ef3720
For example, if you want to change it to 64 rounds, then
In encryption : delta = 0×9e3779b9
In decryption : delta = (0×9e3779b9 x 64)% 0xffffffff = 0×8dde6e40
it hope it helps. please tell me whether this tweak works or not.
Comment by edipermadi — 11 March 2009 @ 10:13 am
Bonjour
Je ne sais pas moi-même comment faire pour décrypter
Ni comment il a était crypte.
Je vous serai très reconnaissant si vous trouvez.
Peut être qu’au niveau des logiciels est une fois
Désassemble il y a la routine de décryptage.
Merci de votre aide
Hello
I do not know myself how to decrypt
Or how it was a crypt.
I shall be very grateful if you find.
May be that level of software is once
Disassembler there is the decryption routine.
Thank you for your help
Comment by paul — 11 March 2009 @ 4:56 pm
@paul :
i have spent my time to guess what is going on actually in your application. that was hard. sorry to say, i cannot give you any solution. perhaps, reversing from the code would be easier. i really appologize for this.
Comment by edipermadi — 12 March 2009 @ 9:38 am
Hello
And thank you again for your help, I think he has a bit of encryption
And generate random characters to scramble and make decoding difficult.
But you’ve written a routine encryption?
The I work on a program for Pic 162628 and I looking for a routine
in basic or assembler which I will encrypt the data before stored in eeprom.
Thank you
Bonjour
Et encore merci de votre aide, moi je pense qu’il a un peut de cryptage
Et des caractères génèrent aléatoirement pour brouiller et rendre difficile le décodage.
Mais vous vous avez écris une routine de cryptage ?
La je travail sur un programme pour un Pic 162628 et je cherche une routine
en basic ou assembleur qui va me crypter les données avant de stockée dans l’eeprom.
Merci
Comment by paul — 12 March 2009 @ 4:51 pm
@edipermadi:
It works!! I tried what you said and it can work for any number of rounds..:) Many many thanks!!!
Comment by Shirley G — 13 March 2009 @ 12:05 am
@Shirley G :
Congratulation,,
@paul :
i guess, decrypting something is a matter of algorithm. in the other words, we should use decryption routine which is the inverse of encrypting routine. the next problem is to guess how the data was encrypted. and that is the reason why decryping an unknown algorithm is a tough question. this problem must be solved by cryptanalysis.
Comment by edipermadi — 13 March 2009 @ 9:40 am
Hello
I know this is not easy to find it so he was
Encrypted.
And you even know write programs for microcontrollers?
If yes what language.
Good luck
Bonjour
Je sais que ce n’est pas facile de trouver de qu’elle manière il a était
Cryptée.
Et vous-même savez écrire des programmes pour microcontrôleurs ?
Si oui avec quel langage.
Bon courage
Comment by paul — 13 March 2009 @ 5:13 pm
@paul :
dude, sorry to say. i tried once again to reveal the algorithm you supplied, but i have no idea at all. it probably written in C, assembly of basic. but all language are resulting the same thing which is native code for microcontroller anyway. so i cannot guarantee which language is used in that case.
Comment by edipermadi — 19 March 2009 @ 9:51 am
Hello
Thank you for your help, you know your own schedule pics?
Because I need a routine for my encryption program on a pic
16f628A I go to basic language pro.
http://www.microengineeringlabs.com/
so if you know using this compiler?
Thank you
Comment by paul — 19 March 2009 @ 5:18 pm
@paul:
i coded several cipher algorithm. all of them were coded in assembly language. most most them were focused on PIC16 while a small part belong to PIC18. You can check it out on http://cryptonutter.googlecode.com
i’m not familiar to basic compiler ;p
basically basic programming is easy you could use it without any problem. OK, good luck
Comment by edipermadi — 23 March 2009 @ 9:52 am
hello…can you explain how the TEA algorithm works and diagram above pls?We use the TEA algorithm on our thesis title “a file encryption and decryption system”…We are having hard time to defend it,and we will redefend it one more time on Oct.26,2009…It will be our last chance or else we will failed our thesis 1.They are asking what is the green box,the red circle,the shifts,the delta,and what is the explanation for k(0) to k(3)and why it has left and right?how it process step by step?Please Please help us…God bless…
Comment by Ysa — 20 October 2009 @ 11:44 am
hello…can you explain how the TEA algorithm works and diagram above pls?We use the TEA algorithm on our thesis title “a file encryption and decryption system”…We are having hard time to defend it,and we will redefend it one more time on Oct.26,2009…It will be our last chance or else we will failed our thesis 1.They are asking what is the green box,the red circle,the shifts,the delta,and what is the explanation for k(0) to k(3)and why it has left and right?how it process step by step?Please Please help us…God bless…thanks for the help in advance…
Comment by Ysa — 20 October 2009 @ 12:26 pm
@Ysa
hello..Ysa, i’ll send you the explanation about TEA through your yahoo email. i hope i could mail it tomorrow.
Comment by edipermadi — 20 October 2009 @ 5:00 pm
Dear Edipermadi,
Thank you so much for the email that you send me about the TEA Algorithm..I will study it and hopefully I can explain it well to our panelist…
Again,thank you for the help…
Comment by Ysa — 23 October 2009 @ 9:17 pm
BIG BIG THANKS FOR THE BIG BIG HELP
Comment by Ysa — 23 October 2009 @ 9:20 pm