Tiny encryption algorithm

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 11/16/2014 Tiny Encryption Algorithm 2

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. 11/16/2014 Tiny Encryption Algorithm 3

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 11/16/2014 Tiny Encryption Algorithm 4

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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. 11/16/2014 Tiny Encryption Algorithm 6

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. 11/16/2014 Tiny 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; } 11/16/2014 Tiny Encryption Algorithm 8

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; } 11/16/2014 Tiny Encryption Algorithm 9

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 */ } } 11/16/2014 Tiny Encryption Algorithm 10

11. Thank you 11/16/2014 Tiny Encryption Algorithm 11