TruWallet: Trustworthy and Migratable Wallet-Based Web Authentication

RuhR-University Bochum System Security Lab

TruWallet: Trustworthy and Migratable
Wallet-Based Web Authentication

Sebastian Gajek1, Hans Löhr2, Ahmad-Reza Sadeghi2,
Marcel Winandy2

Tel Aviv University, Israel
1
2
Ruhr-University Bochum, Germany

ACM STC 2009 – 4th Annual Workshop on Scalable Trusted Computing
Chicago, Illinois, USA – November 13, 2009


Introduction
● Identity theft is a growing crime on the Internet
(especially phishing)
● Classical phishing: faked web sites
password

password

Adversary A Phishing Server

● Malware phishing: attacking user's device

password

password

Adversary A Phishing Server

Marcel Winandy TruWallet: Wallet-Based Web Authentication (STC 2009) 2009-11-13 2


Introduction
● Countermeasures against phishing
– A broad range of approaches exists
● Promising: “wallet” (authentication agent)
– Stores all user login credentials
– Authenticates web sites for their legitimacy
– Performs login on behalf of user

+



Introduction
● However: needs strong protection mechanism
(malware could attack wallet directly)



Introduction
● We have trusted computing – so what?
(secure boot, sealing, attestation, etc.)



Introduction
● We have trusted computing – so what?
(secure boot, sealing, attestation, etc.)
● Scalability issues:
– PKI dependency: server can change SSL certificate
(update, new CA, new URL, etc.)
– Device restriction: wallet locked-down to one platform



TruWallet - Overview
● High-level architecture
● Automated login with SSL-PKI-independent
server authentication
● Secure migration of wallet data to other devices
● Implementation



TruWallet Architecture



SSL-PKI-Independent Server
Authentication



Authentication
● Registration (user creates new account)



Authentication
– TruWallet creates high-entropy password

new password



Authentication
– Derive shared secret from server_finished

client_hello

SSL handshake

encSSL(server_finished)



Authentication

client_hello

SSL handshake

shared shared
secret encSSL(server_finished) secret



Authentication

new password client_hello

SSL handshake

shared shared
secret encSSL(server_finished) secret

Link password with shared secret (and server URL)



Authentication
● Login (user connects to registered account)
– Server is authenticated via challenge-response

client_hello

SSL handshake




Authentication

nonce
client_hello

SSL handshake




Authentication

nonce
client_hello

SSL handshake

encSSL(server_finished || HMACsharedsecret(trnscrpt))



Authentication

nonce
client_hello

SSL handshake shared
secret
shared
secret encSSL(server_finished || HMACsharedsecret(trnscrpt))

Only if server can prove knowledge of shared secret, user password is sent.



Secure Migration of Wallet Data



Secure Migration of Wallet Data
● Another Wallet on destination platform
● Establish a trusted channel between platforms
– Secure channel (confidentiality)
– Bound to TCB configuration of destination
● Send wallet data through trusted channel
● Trusted Channel based on [Asokan+2007],
– But here: less components, less steps



Migration Protocol
Source platform Destination platform
Storage Trust Storage
Manager Wallet Wallet TPM
Manager Manager
requestTrustedChannel() request-
TrustedChannel() TPM_CreateWrapKey()
ESKBind:=
encrypt_SRK(SKBind,TCBconf)
(PKBind, ESKBind)

TPM_CertifyKey(PKBind)

certBind
(certBind, PKBind, ESKBind)
(certBind, PKBind)

verify(certBind)
loadData()
wd
ewd :=
Tspi_Data_Bind(PKBind,wd)
ewd TPM_LoadKey(ESKBind)
unbind(ewd)

TPM_Unbind(ewd)
verify(TCB_conf)
SKBind:= decrypt_SRK(ESKBind)
wd:= decrypt_SKBind(ewd)
wd wd
storeData(wd)



Migration Protocol
Manager Manager
ESKBind:=
(PKBind, ESKBind)


certBind
(certBind, PKBind)

verify(certBind)
loadData()
wd
ewd :=
unbind(ewd)

TPM_Unbind(ewd)
verify(TCB_conf)
wd wd
storeData(wd)



Implementation
● Security Kernel: Turaya/L4
– L4 microkernel
– security services
● TruWallet:
– Java implementation
– Uses Paros HTTP/HTTPS Proxy
– Running in a Linux VM
● Web Browser:
– Firefox, running in separate Linux VM



Implementation Overview
Linux Linux
Virtual Machine Virtual Machine

Firefox
Paros Wallet

Network Storage Trust
mGUI Security Kernel
Mgr Mgr Mgr
(Turaya)
L4 microkernel

Hardware TPM



Linux Linux

Firefox
Paros Wallet

Mgr Mgr Mgr
(Turaya)
L4 microkernel

Hardware TPM
Video NIC Disk



Linux Linux

Firefox
Paros Wallet

Mgr Mgr Mgr
(Turaya)
L4 microkernel

Hardware TPM
NIC



Conclusion
● Phishing is a serious threat
● Wallets can perform login on behalf of user
● TruWallet provides:
– Secure execution environment
– Server authentication with less SSL PKI dependency
– Secure migration to other computing devices
● Prototype based on L4 microkernel and virtualization
● Future work:
– TruWallet on dynamic root of trust (Intel TXT)



Questions?

Marcel Winandy
Ruhr-University Bochum
marcel.winandy@trust.rub.de


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