Tiny encryption algorithm

1. Tiny Encryption Algorithm
(TEA)
Presented by Farah Al-Tufaili

2. Introduction
 The Tiny Encryption Algorithm (TEA) is one of the fastest and most efficient
cryptographic algorithms in existence.
 The Tiny Encryption Algorithm (TEA) is a symmetric (private) key encryption
algorithm created by
 David Wheeler and Roger Needham of Cambridge University and published in
1994
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3. OVERVIEW OF TEA
 TEA is a symmetric key algorithm.
 TEA is designed to minimize memory footprint and maximize speed.
 It is a Feistel type cipher
 Achieves the Shannon's properties of complete diffusion and confusion with
out the employment of S & P boxes, after only six rounds but thirty two
rounds are recommended.
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4. FUNCTIONALITY OF TEA
 Inputs to encryption algorithm are 64 bits of plain/cipher text , 128 bits of
key and output is a cipher/plain text.
 It performs operations on 32 bit words.
 Each round has 4 sub key k[i].
 Each half of message is used to encrypt the other half over 64 rounds of
processing and then combine to produce the cipher text block.
 A half block is processed and swapped iteratively and all operations are
performed on modulo 32‐bit
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5. 3/14/2015Tiny Encryption Algorithm 5

6. OPERATIONS PERFORMED IN A SINGLE
ITERATION
 Each round i has inputs Left[i-1] and Right[i-1], derived from the previous
round, as well as a sub key K[i] derived from the 128 bit overall K.
 The sub keys K[i] are different from K and from each other.
 Delta is defined as a constant, 2^32/(golden ratio), which is 2654435769 as an
integer.
 Multiples of delta are used in each round (mod 2^32), Delta is derived from
the golden number ratio to ensure sub keys to be different.
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7.  In the first feistel round R is used as
an input to several operations. All
addition operations are (mod 2^32).
 1. R goes through a left shift of 4 and
then is added to K[0]
 2. R is added to Delta
 3. R goes through a right shift of 5 and
then is added to K[1]
 An XOR operation is then applied to
the result of those three operations
and finally, the result of
 the XOR operation is added to L. This
result then becomes R for the next
feistel round, because of the swap.
3/14/2015Tiny Encryption Algorithm 7
TEA has a 128 bit key that is split up into
four 32 bit subkeys, which can be seen as
K[3]in the diagram.
Delta is defined as a constant, 2^32/(golden
ratio), which is 2654435769 as an integer.
Multiples of delta are used in each round
(mod 2^32).

8. TEA Encryption Function
 void encrypt(unsigned long k[], unsigned long text[]) {
 unsigned long y = text[0], z = text[1];
 unsigned long delta = 0x9e3779b9, sum = 0; int n;
 for (n= 0; n < 32; n++) {
 sum += delta;
 y += ((z << 4) + k[0]) ^ (z+sum) ^ ((z >> 5) + k[1]);
 z += ((y << 4) + k[2]) ^ (y+sum) ^ ((y >> 5) + k[3]); }
 text[0] = y; text[1] = z; }
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9. TEA decryption function
 void decrypt(unsigned long k[], unsigned long text[]) {
 unsigned long y = text[0], z = text[1];
 unsigned long delta = 0x9e3779b9, sum = delta << 5; int n;
 for (n= 0; n < 32; n++) {
 z -= ((y << 4) + k[2]) ^ (y + sum) ^ ((y >> 5) + k[3]);
 y -= ((z << 4) + k[0]) ^ (z + sum) ^ ((z >> 5) + k[1]);
 sum -= delta;
 }
 text[0] = y; text[1] = z;
 }
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10. TEA in use
 void tea(char mode, FILE *infile, FILE *outfile, unsigned long k[]) {
 /* mode is ’e’ for encrypt, ’d’ for decrypt, k[] is the key.*/
 char ch, Text[8]; int i;
 while(!feof(infile)) {
 i = fread(Text, 1, 8, infile); /* read 8 bytes from infile into Text */
 if (i <= 0) break;
 while (i < 8) { Text[i++] = ' ';} /* pad last block with spaces */
 switch (mode) {
 case 'e': encrypt(k, (unsigned long*) Text); break;
 case 'd':decrypt(k, (unsigned long*) Text); break;
 }
 fwrite(Text, 1, 8, outfile); /* write 8 bytes from Text to outfile */
 }
 }
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11. Thank you
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