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AS 2805.5.2-2009 pdf free download

AS 2805.5.2-2009 pdf free download.Electronic funds transfer Requirements for interfaces Part 5.2: Ciphers Modes of operation for an n-bit block cipher.
The Ol)erat iou of encrypting each 1)laIuIt(xt varml)le euuIl)l03’s the followitig six ste1x4.
a) X1 = n FR1 (Select ion of left most. n bits of FR).
1)) = cK(Xe) (Use of l,lock cipher).
c) E = j Y (Selection of leftmost j bits of YE).
d) C’ = P, E, (Generation of ciplwrtext variable).
e) F = I(k — j) I C (Generation of feedback variable).
1) Fl)141 = Sk(FB1 F1) (Shift function on FB).
These steps are repeated for i = 1,2 q. en(lmg with step (d) on the last cycle. The procedure is shown in the left side of figure C.3. The leftmost j bits of the output block V of the block cipher are used to encrypt the j-bit plaintext variable by niodttlo 2 addition. The remaining bits of V are discarded. The plaintext and ciphertext variables have bits tiuimbered from 1 to j.
The ciphertext variable is augniented by placing k — j one bits in its leftmost bit positions to l)ec()1iw the k—bit feedback variable F. Then the bits of the feedback buffer Fl) are shifted left by k places amid F is inserted in the rightmost k places, to Pro(lLm(e the new value of the feedback buffer F!?. In this shift, operation. time leftmost k bits of F!? are discarded. Thii new ia left most bits of FL? are used as the next input X of the encryption process.
8.3 Decryption
The variables employed for (lecryption are the same as those employed for encryptioii.
The feedback buffer F!) is set to its initial value
FB1 = SV
The operation of decrypting each ciphertext variable employs the following six steps.
a) X1 = n FR1 (Selection of leftmost ii bits of Fl)).
b) YE = e,(X,) (Use of block cipher).
c) E, = j Y (Selection of leftmost j bits of 1),
d) P = c1 e E1 (Generation of plaintext variable).
e) F = I(k — j) C (Generation of feedback variable).
f) FB± = Sk(FBI I F1) (Shift function on FR).AS 2805.5.2-2009 pdf free download.

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