Q4. (16 points). Explain the difference between CFB and OFB modes of block cipher operation. What mode is more reliable? Why? Hints: 2. IV IV ON- . SS 60 K Encrypt Encrypt Expl K Encrypt Encrypt 14 Encrypt 164 Lord He PM C CM C (a) Encryption C CM C (a) Encryption IV - . IV O You 194 ST SA her Encrypt Ener Ys Decrypt . Encrypt 164 Encrypt you Dhard Decrypt 64 . Sabun Terd 61 - -C, C P PM P3 bi Decryption Figure 3.13 s-bit Cipher Feedback (CFB) Mode PI PM P2 (1) Decryption Figure 3.14 s-bit Output Feedback (OFB) Mode CN- IV ON- IV Singer Singh Si regler 64-bit 64 register 64-bits bits Shinregter 64-bits bits SH Ngister 64 K KEncrypt KEncrypt 164 Encrypt 164 KEncrypt KEncrypt 764 KEncrypt 164 Select WIN Dan4 Select Select Dincard Select Dhcard Select Discard 64-bits P P2 Select bits 23 P2 PM CM C (a) Encryption (a) Encryption IV CMA1 in register Shinregister Singh 56 ON-1 64 Shin register Shr 64-bits Sanger K Encrypt K-Decrypt 64 KEnerypt 164 K Encrypt K Decrypt Select Dhcard Select Encrypt 64 card Dhcard bits Select Select Dhcard Select Dhcard 64 bits Discard 64-bits CM P2 (b) Decryption Figure 3.13 s-bit Cipher Feedback (CFB) Mode P1 PM P2 (b) Decryption Figure 3.14 s-bit Output Feedback (OFB) Mode Q4. (16 points). Explain the difference between CFB and OFB modes of block cipher operation. What mode is more reliable? Why? Hints: 2. IV IV ON- . SS 60 K Encrypt Encrypt Expl K Encrypt Encrypt 14 Encrypt 164 Lord He PM C CM C (a) Encryption C CM C (a) Encryption IV - . IV O You 194 ST SA her Encrypt Ener Ys Decrypt . Encrypt 164 Encrypt you Dhard Decrypt 64 . Sabun Terd 61 - -C, C P PM P3 bi Decryption Figure 3.13 s-bit Cipher Feedback (CFB) Mode PI PM P2 (1) Decryption Figure 3.14 s-bit Output Feedback (OFB) Mode