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Lecture 5 Block Diagrams Modes of Operation of Block Ciphers. Modes of Operation of Block Ciphers. Block vs. stream ciphers. M 1 , M 2 , …, M n. m 1 , m 2 , …, m n. Internal state - IS. Block cipher. K. K. Stream cipher. C 1 , C 2 , …, C n. c 1 , c 2 , …, c n. C i =f K (M i ).
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Lecture 5 Block Diagrams Modes of Operation of Block Ciphers
Modes of Operation of Block Ciphers ECE 448 – FPGA and ASIC Design with VHDL
Block vs. stream ciphers M1, M2, …, Mn m1, m2, …, mn Internal state - IS Block cipher K K Stream cipher C1, C2, …, Cn c1, c2, …, cn Ci=fK(Mi) ci = fK(mi, ISi) ISi+1=gK(mi, ISi) Every block of ciphertext is a function of the current block of plaintext and the current internal state of the cipher Every block of ciphertext is a function of only one corresponding blockof plaintext
Typical stream cipher Sender Receiver initialization vector (seed) initialization vector (seed) key key Pseudorandom Key Generator Pseudorandom Key Generator keystream ki keystream ki mi ci ci mi plaintext ciphertext ciphertext plaintext
Standard modes of operation of block ciphers Block cipher turned into a stream ciphers Block cipher ECB mode Counter mode CFB mode CBC mode
Electronic CodeBook Mode – ECB Encryption K K K K M3 M1 M2 MN MN-1 K E E E E E . . . C3 C1 C2 CN CN-1 Ci = EK(Mi) for i=1..N
Electronic CodeBook Mode – ECB Decryption K K K K C3 C1 C2 CN CN-1 K D D D D D . . . M3 M1 M2 MN MN-1 Mi = DK(Ci) for i=1..N
Electronic CodeBook Mode – ECB (simplified block diagram) Mi Ci Ci = EK(Mi) Mi = DK(Ci) IN IN K K E D OUT OUT Ci Mi
Electronic CodeBook Mode – ECB (combined block diagram) bdi IN IN K K E D OUT OUT bdi = Mi for Encryption Ci for Decryption bdo bdo = Ci for Encryption Mi for Decryption
Counter Mode - CTR Encryption K K K K IV+N-1 IV+N-2 IV IV+1 IV+2 . . . K E E E E E . . . kN kN-1 k2 k3 k1 mN mN-1 m2 m3 m1 c2 cN-1 c3 cN c1 ci = mi ki ki = EK(IV+i-1) for i=1..N
Counter Mode - CTR Decryption K K K K IV+N-1 IV+N-2 IV IV+1 IV+2 . . . K E E E E E . . . kN kN-1 k2 k3 k1 cN cN-1 c2 c3 c1 m2 mN-1 m3 mN m1 mi = ci ki ki = EK(IV+i-1) for i=1..N
Counter Mode – CTR (simplified block diagram) IV IV IS1 = IV ci = EK(ISi) mi ISi+1 = ISi+1 IS1 = IV mi = EK(ISi) ci ISi+1 = ISi+1 counter counter ISi ISi IN IN K K E E OUT OUT ci ci mi mi
Counter Mode – CTR (combined block diagram) IV bdi = mi for Encryption ci for Decryption counter ISi IN bdo = ci for Encryption mi for Decryption K E OUT bdo bdi
Cipher Feedback Mode - CFB Encryption IV . . . E E E E E . . . k3 kN k1 k2 kN-1 mN mN-1 m3 m1 m2 c2 cN-1 c3 cN c1 ci = mi ki ki =EK(ci-1) for i=1..N, and c0 = IV
Cipher Feedback Mode - CFB Decryption IV . . . E E E E E . . . k3 kN k1 k2 kN-1 mN mN-1 m3 m1 m2 c2 cN-1 c3 cN c1 mi = ci ki ki =EK(ci-1) for i=1..N, and c0 = IV
Cipher Feedback Mode – CFB (simplified block diagram) IV IV register IS1 = IV ci = EK(ISi) mi ISi+1 = ci register ISi ISi IN IN K K E E IS1 = IV mi = EK(ISi) ci ISi+1 = ci OUT OUT ci ci mi mi
Cipher Feedback Mode – CFB (combined block diagram) IV bdi = mi for Encryption ci for Decryption register ISi bdi IN bdo = ci for Encryption mi for Decryption K E OUT bdo bdi
Cipher Block Chaining Mode - CBC Encryption m3 m1 m2 mN mN-1 . . . IV E E E E E . . . cN c1 cN-1 c2 c3 ci = EK(mi ci-1) for i=1..Nc0=IV
Cipher Block Chaining Mode - CBC Decryption cN c1 cN-1 c2 c3 D D D D D . . . . . . IV m3 m1 m2 mN mN-1 mi = DK(ci) ci-1for i=1..Nc0=IV
Cipher Block Chaining Mode – CBC (simplified block diagram) IV IN register K IS1 = IV ci = EK(ISi mi) ISi+1 = ci IS1 = IV mi = DK(ci) ISi ISi+1 = ci D ISi mi OUT IN mi K E ISi register OUT ci ci IV
Cipher Block Chaining Mode – CBC (combined block diagram) bdi IV ci IN K D register bdi ISi OUT bdi IN K E OUT bdo
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AES_Enc • Encryption Only • Key scheduling done as a part of initialization
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AES_Enc_KOF • Encryption Only • Key scheduling done On the Fly
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AES_EncDec • Encryption and Decryption • Key scheduling done as a part of initialization
AES_EncDec: Interface with the Division into the Datapath and Controller
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