Talk:CAST-128

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Cast-128 Image[edit]

Hello,

i am writing about an image you created for the article about the Cast-128 crypto algorithm. As i studied the specific algorithm, i realized that there is a slight difference between the image and the Request For Comments 2144 where the algorithm is presented. Copying form the RFC:

      Type 1:  I = ((Kmi + D) <<< Kri)
               f = ((S1[Ia] ^ S2[Ib]) - S3[Ic]) + S4[Id]

      Type 2:  I = ((Kmi ^ D) <<< Kri)
               f = ((S1[Ia] - S2[Ib]) + S3[Ic]) ^ S4[Id]

      Type 3:  I = ((Kmi - D) <<< Kri)
               f = ((S1[Ia] + S2[Ib]) ^ S3[Ic]) - S4[Id]

The RFC also states:

  "CAST-128 uses a pair of subkeys per round:  a 32-bit quantity Km is
  used as a "masking" key and a 5-bit quantity Kr is used as a
  "rotation" key."

So i believe that the two sub-keys (Kmi and Kri) should be switched in place in the image. I believe that now the image depicts the opposite argument.

Test Vectors[edit]

Moved here from the article (Removed in this edit). Wikipedia is not the place for reference documentation like this. -- Sverdrup (talk) 11:55, 6 March 2013 (UTC)[reply]

Test vectors :

Below is a sample test vector, providing the input and the expected output for the above algorithm. Even, the values of Key Schedule, Km and Kr is provided for both encryption and decryption.

Encryption :

128-bit key = 01 23 45 67 12 34 56 78 23 45 67 89 34 56 78 9A
plaintext   = 01 23 45 67 89 AB CD EF
ciphertext  = 23 8B 4F E5 84 7E 44 B2

i	K[i]	Km[i]	Kr[i]
1	BC173E26	BC173E26	00000015
2	78A207EF	78A207EF	0000001B
3	ECE0A7F5	ECE0A7F5	00000001
4	7CB0FB6B	7CB0FB6B	00000005
5	A5D2D636	A5D2D636	00000003
6	D78B9407	D78B9407	0000001F
7	56C069D3	56C069D3	0000001F
8	82E8240C	82E8240C	0000001C
9	33543749	33543749	00000010
10	8813D5C7	8813D5C7	0000001F
11	B9FCD732	B9FCD732	00000012
12	59106B36	59106B36	00000001
13	496AF1A9	496AF1A9	0000001D
14	18F8DC43	18F8DC43	00000019
15	8D9DEF0F	8D9DEF0F	00000001
16	83EDA384	83EDA384	0000000F

Decryption :

128-bit key = 01 23 45 67 12 34 56 78 23 45 67 89 34 56 78 9A
plaintext   = 23 8B 4F E5 84 7E 44 B2
ciphertext  = 01 23 45 67 89 AB CD EF

i	K[i]	Km[i]	Kr[i]
1	BC173E26	BC173E26	00000015
2	78A207EF	78A207EF	0000001B
3	ECE0A7F5	ECE0A7F5	00000001
4	7CB0FB6B	7CB0FB6B	00000005
5	A5D2D636	A5D2D636	00000003
6	D78B9407	D78B9407	0000001F
7	56C069D3	56C069D3	0000001F
8	82E8240C	82E8240C	0000001C
9	33543749	33543749	00000010
10	8813D5C7	8813D5C7	0000001F
11	B9FCD732	B9FCD732	00000012
12	59106B36	59106B36	00000001
13	496AF1A9	496AF1A9	0000001D
14	18F8DC43	18F8DC43	00000019
15	8D9DEF0F	8D9DEF0F	00000001
16	83EDA384	83EDA384	0000000F

Attack vectors?[edit]

One topic found in other crypto articles is a section discussing known or suspected attack vectors. Even for ciphers considered secure, cryptanalysis research might suggest theoretical avenues of attack, and this would be interesting to note in the article for anyone researching the cipher. Any experts care to add? 137.254.4.10 (talk) 23:09, 13 February 2015 (UTC)[reply]