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A video authentication scheme for H.264/AVC Main profile

Nandakishore RamaswamyMultimedia Processing Lab

July 9th, 2004.

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Agenda Objectives Introduction Previous work Encoder/Decoder description Simulation Results Conclusion and Future work References

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Objectives Verify the integrity of the video

bitstream compressed by H.264/AVC Main Profile

Identify the originator (sender) of the video

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Introduction Multimedia authentication: - Verify

the integrity of the multimedia signala) Hard authentication: - Allows no alteration of

the pixel values. b) Soft authentication: - Accepts manipulations of

the pixel values which preserve the semantic structure of the multimedia signal.

Typically, cryptographic techniques are used for authentication and verification.

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Digital Signature Vs Encryption Digital Signature Alice wants to sign and send a message to Bob

Encryption algorithm

BobMessages match

Alice’s private key

Digital Signature

Alice’s public key

Received Digital Signature

Original Message

Received Message

Encryption algorithm

Alice

Yes = Signature VerifiedNo= Signature Verification failed

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Digital Signature Vs Encryption (contd.) Encryption Alice wants to encrypt and send a message to Bob

Encryption algorithm

Bob

Bob’s public key

Cipher message

Bob’s private key

Received cipher message

Original Message

Original MessageEncryption algorithm

Alice

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Introduction (contd.) A generic video authentication process [1]

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Introduction (contd.) A generic video verification process [1]

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Digital Signature Standard Digital signature standard (DSS) a) Developed by NIST b) Consists of two parts - Secure Hash Algorithm (SHA)

- Digital Signature Algorithm (DSA)

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(DSA and SHA)’s relationship

Secure Hash Algorithm

DSA Sign operation

Secure Hash Algorithm

DSA Verify Operation

Signature

Original Message

Received Message

Message Digest Message Digest

Private Key

Public Key

Yes = Signature VerifiedNo= Signature Verification failed

Signature Generation

Signature Verification

Source:- Federal Information Processing Standards Publications –180http://www.itl.nist.gov/fipspubs/fip180-1.htm

160 bits 160 bits

320 bits 320 bits

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Rivest Shamir and Adleman (RSA) EncryptionLet m = Input Message

e = Encrypted messagen = Common parameterpr = Private Keypb = Public Key

Encryptione = mpr * mod(n) Decryptionm = epb * mod(n)

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Previous Work Digital signature generation using block means [2]

Division into 8x8 blocks

Block mean

computation

Quantization

Encryption

Original Image Sender’s

secret keyDigital

Signature

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Previous Work (contd.) Digital signature verification using block means [2]

Division into 8x8 blocks

Extract Block means before inverse quantization

Decryption

Block mean

s matc

hReceive

d Image

Received signatur

eImage

Authentic

Image NOT

AuthenticYes

No

Sender’s

public key

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Previous Work (contd.) Digital signature in JPEG-2000 [3] Every code-block of the compressed image is

hashed using Secure Hash Algorithm and appended at the end of the bitstream.

JPEG-2000 code-block

Compute hash using

SHAEncrypt

using RSA

Sender’s

public key

160 bit digest

Append to bitstream

For verification, received image’s code-blocks are hashed and matched with decrypted hash.

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Encoder/Decoder description

A video authentication scheme for H.264/AVC Main

profile

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Encoder Luma values only Features taken in transform

domain Intra and Inter MB’s Signature for every coded video

sequence

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Encoder (contd.) Intra 4x4 and Inter MB

DC

AC

AC

(0,0)

(3,0)

(0,3)

(3,3)

(3,0) (3,3

)

(0,3)

(0,0)

Q

4X4 integer DCT

T

Original residual block

Transformed and quantized blockFeature data

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Encoder (contd.) Intra 16x16 MB

T

Q

T4X4 integer DCT

4X4 Hadamard transform

Original 16x16 MB residual

Transformed 16x16 MB

Quantized Hadamard coefficients

Q

Feature data

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Encoder (contd.) Collect all feature data of a MB for

every picture. Insert picture number after a

picture is coded Repeat process until end of

sequence

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Encoder (contd.)

Feature data Hash (SHA)

Generate signature D=DSA(H)

Encryption E= RSA(D)

Sender’s private key

Receiver’s public key

Append as SEI to video bitstream

Signature generation for a coded video sequence

H

D

E

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Encoder (contd.) Multiple signature generation

a) Video = 1 or more video sequencesb) Generate signature for every video sequence

c) Append every signature as SEI in the corresponding video sequence

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Decoder (contd.) Luma values only

Features taken in transform domain

Signature verification for every coded video sequence

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Decoder (contd.) Intra 4x4 and Inter MB’s

DC

AC

AC

(0,0)

(3,0)

(0,3)

(3,3)4x4 block of transform

coefficients before inverse quantization

Feature data

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Decoder (contd.) Intra 16x16 MB

Transformed 16x16 MB before inverse quantization

Hadamard coefficients before inverse quantization

15 AC coefficients

Feature data

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Decoder (contd.) Collect all feature data of a MB for

every picture.

Insert picture number after a picture is decoded

Repeat process until end of sequence

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Decoder (contd.) Signature verification for a coded

video sequence

Feature data Hash (SHA)

Verify signature D’’ = DSV(H’,D’)

Decryption D’=RSA-1(E’)

Received video and signature

D’’=D’

Sender’s public key

Receiver’s private key

Video Authenticated

Video NOT Authenticated

E’

D’

D’’

H’

YesNo

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Decoder (contd.) Tampering frames = Signature failure Sender forgery = Signature failure Cannot point out the reason of

signature failure If tampered, cannot point out location

of tampering Modify encoder to accommodate

these issues

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Revised Encoder Compute hash of every picture in the

coded video sequence. Signature failure = Match decoder

hash Inter and Intra for hash computation Transform domain values only Luma frames Authentication data = Signature +

Hash

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Hash computation Intra 4x4 and Inter MB

DC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

(0,0)

(3,0)

(0,3)

(3,3)

(3,0) (3,3

)

(0,3)

(0,0)

Q

4X4 integer DCT

T

Original residual block

Transformed and quantized blockFeature data

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Hash computation (contd.) Intra 16x16 MB

T

Q

T4X4 integer DCT

4X4 Hadamard transform

Original 16x16 MB residual

Transformed 16x16 MB

Quantized Hadamard coefficients

Q

Feature data

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Hash computation (contd.)

Feature data for a picture

Hash PH =

SHA(data)

Encryption EH= RSA(PH)

Receiver’s public key

Append as SEI to video bitstream

Hash generation for a picture

PH

EH

Repeat process for every picture in the coded video sequence

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Tampered locations and sender forgery

Signature Failure

Decrypt hashes

Compute Hash for every picture

All Hashe

s match

?

Signature failure due to sender

forgery

Signature failure due to

tampering. (Identify tampered

locations)

Receiver’s private key

YesNo

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Decoder Hash Computation Intra 4x4 and Inter MB: - DC and

AC coefficients of every 4x4 block before inverse quantization

DC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

(0,0)

(3,0)

(3,3)

(0,3)

4x4 block of transform coefficients before inverse quantization

Feature data

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Decoder Hash Computation (contd.) Intra 16x16 MB

Transformed 16x16 MB before inverse quantization

Hadamard coefficients before inverse quantization

15 AC coefficients

Feature data

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Simulation Results

A video authentication scheme for H.264/AVC Main

profile

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DSA common parameters Private Key932308816105877193346324924405238358561797363453 Public Key49250364518976760201935612031242625664970300784488999206628

913898684885553279548885211476769179063848086265981390552828860770995411616739007429069330033064008697384549473384637876060915808531747270579608164016570165925297909070695052210446426918824013612814674507994466578915575028597282519755964472561590380

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Results for one coded video sequence Common ParametersTotal frames encoded = 59Total coefficients = 12501Encoder signaturer = 258230994199886379618680381531392644375747268307 s = 553921005467375065529673563440116158716908054793 Without tampering or forgeryDecoder Signaturev = 258230994199886379618680381531392644375747268307Since r = v, signature is verified.

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Results for one coded video sequence (contd.) Frame tamperingFrame 0 = I frame = tamperedLocation = 1st Intra 16x16 block, DC coefficient at (0,0) after

Hadamard transform and quantizationOriginal value = 5Modified value = 15

Decoder signaturev = 363510879679629003962752313295967888200812862057 But r =

258230994199886379618680381531392644375747268307 Since, r is not equal to v, Signature is NOT verified.

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Results for one coded video sequence (contd.) Hash of all pictures in the video

sequence are compared.Picture 0

Encoder Hash = 244521134779192871239422005322433514569730613982 Decoder Hash = 564856327811211747778209339112070483726931840033

Hashes are NOT equal. Tampered location = Picture 0

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Results for one coded video sequence (contd.) Detecting malicious activity Private key used to sign video = Imposter’s Public key used to verify = Legal user’s

Original Private Key = 932308816105877193346324924405238358561797363453

Imposter’s private key = 13230881610587719334632492440523835856179736345

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Results for one coded video sequence (contd.) Encoder signaturer = 258230994199886379618680381531392644375747268307 s = 659115584368708655163218960845447884312706027895

Decoder signaturev = 757611328353143787983558147251463660400321700712

Since r is NOT equal to v, signature is NOT verified.

Encoder hashes = Decoder hashesThus, signature failure due to malicious

activity.

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Results for one coded video sequence (contd.) Robustness to quantizationSequence is encoded with QP 29

Encoder signaturer = 258230994199886379618680381531392644375747268307 s = 553921005467375065529673563440116158716908054793

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Results for one coded video sequence (contd.) Sequence is re-encoded with QP 35

Decoder signaturev = 450045542578458967124875488958087354781835818707 Since r is NOT equal to v, Video is NOT authenticated.

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Results for one coded video sequence (contd.) Frame reordering attack Original Re-ordered

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Results for one coded video sequence (contd.) DC Attack : - Block mean kept the same but

values modified.

Original Block

Transformed Block

Quantized Block

Modified Block

Transformed Block

Quantized Block

T Q

T Q

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Results for one coded video sequence (contd.)

When using only DC coefficientEncoder Signature (Original Block)

Decoder Signature (Modified Block)

Video is authenticated (Signatures match) even though the block has changed!

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Results for one coded video sequence (contd.)

When using DC and AC coefficientsEncoder Signature (Original Block)

Decoder Signature (Modified Block)

Video is NOT authenticated. Robust to DC attack!

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Results for one coded video sequence (contd.) Encoder signaturer = 258230994199886379618680381531392644375747268307 s = 553921005467375065529673563440116158716908054793

Decoder signaturev = 796457292123352592426447215935643118188436156788

Since r is NOT equal to v, signature is NOT verified.

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Results for multiple coded video sequence (contd.) Total number of frames encoded = 59 Total number of video sequences = 6 Total number of signatures = 6

Encoder Signature 1Total number of coefficients = 4334r = 258230994199886379618680381531392644375747268307 s = 602843151256385963511141755924782867386260766615

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Results for multiple coded video sequence (contd.)Encoder Signature 2Total number of coefficients = 3724r = 258230994199886379618680381531392644375747268307 s = 909298954038809272308410772111508639025580732794

Encoder Signature 3Total number of coefficients = 3896r = 258230994199886379618680381531392644375747268307 s = 37131761566210379177239004151768998162822235640

Encoder Signature 4Total number of coefficients = 4561r = 258230994199886379618680381531392644375747268307 s = 219871236647467187087134837911922129305756281586

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Results for multiple coded video sequence (contd.)Encoder Signature 5Total number of coefficients = 4020r = 258230994199886379618680381531392644375747268307 s = 908124295867495640787368571873172959524293811336

Encoder Signature 6Total number of coefficients = 3860r = 258230994199886379618680381531392644375747268307 s = 954693410128487399463060653092140043143216469688

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Results for multiple coded video sequence (contd.) Decoder Signaturesvi = Signature for ith video sequence

v1 = 258230994199886379618680381531392644375747268307v2 = 258230994199886379618680381531392644375747268307v3 = 258230994199886379618680381531392644375747268307v4 = 258230994199886379618680381531392644375747268307v5 = 258230994199886379618680381531392644375747268307v6 = 258230994199886379618680381531392644375747268307

Signatures match, hence video authenticated

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Storage requirements Signature = Two 160 bit numbers = 320 bitsAfter encryption 1024 bits

Hash of every picture = 160 bitsAfter encryption = 1024 bits

If there are ‘n’ pictures in a video sequenceBits required for hash = 1024 * nTotal bits required = 1024 * (n+1)

If there are ‘x’ coded video sequencesTotal bits required = x * 1024 * (n+1)

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Conclusions Robust to temporal and spatial

manipulations Can detect sender forgery Identifies tamper locations Not robust to quantization Neglect of chrominance

coefficients may lead to attack on chroma components

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Future Work Include chrominance components Requires further research for

robustness to quantization Watermarking the authentication

data directly into the video may result in bit savings

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References1) Atrey, P.K. et al “A hierarchical signature scheme for

robust video authentication using secret sharing”, In Proc of IEEE 10th International Multimedia Modelling Conference, pp. 330-337, 5-7 Jan 2004.

2) Der-Chyuan Lou and Jiang-Lung Liu, “Fault resilient and

compression tolerant digital signature for image authentication”, IEEE Trans. on Consumer Electronics, Vol. 46, pp. 31-39, Feb 2000.

3) Grosbois, R. and Ebrahimi, T., “Secure JPEG 2000-JPSEC”, In Proc of IEEE International Conference on Acoustics, Speech and Signal Processing, Vol. 4 pp. 716-719, 6-10 Apr 2003.

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References (contd.)4) Zhu, B.B., Swanson, M.D., and Tewfik, A.H. "When

seeing isn't believing [multimedia authentication technologies]", IEEE Signal Processing Magazine, Vol.21, pp. 40- 49, Mar 2004.

5) Digital Signature Standard Federal Information Processing Standards

Publication-186http://www.itl.nist.gov/fipspubs/fip186.htm

6) Special Issue on H.264/AVCIEEE Trans. on Circuits and Systems for Video Technology, vol. 13, pp. 557-725, Jul 2003.

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References (contd.)7) Tamhankar, A. and Rao, K.R. “An overview of

H.264/MPEG4- Part 10”, Video/Image Processing and Multimedia Communications, 4th EURASIP, Zagreb, Croatia, 2003.

8) H.264/AVC International Standard ITU‑T Rec. H.264 | ISO/IEC 14496‑10 version 3

9) H.264 Reference softwarehttp://bs.hhi.de/~suehring/tml/

10) YUV 4:2:0 video sequences http://trace.eas.asu.edu/yuv/yuv.html