Effective Design Strategies for Voice Authentication Systems

Best Practices for Voice Authentication Charles R. Jankowski Jr., Ph. D. SpeechTek West 2007 February 21, 2007

Design for Voice Authentication Dialog design is the single most critical aspect of voice authentication performance

Make Verifier SECURE • Make Verifier EASY to use Verifier Dialog and Application Design

Verifier Performance Measures Automation Rate • Percentage of repeat true speakers automated by system • 100 – False Reject Rate • Security Rate • 100 – False Accept Rate

Baseline Performance

Existing ID/Authentication SSN/Account# PIN

Enrollment SSN/Account# PIN 1-9 1-9 1-9 KV selection Optional Used by Verifier

Verification SSN/Account# 1-9 1-9 KV Optional Used by Verifier

Summary of design takeaways • Maintain consistency between enrollment and verification dialogs • Collect enough data during enrollment and verification • Use variable length verification • Use knowledge verification • Use speaker adaptation

Only using 1-9 for voiceprint creation and checking Could also use account number, phone number, etc… Maintain consistency between enrollment and verification SSN/Account# SSN/Account# Authentication 1-9 1-9 1-9 1-9 KV 1-9 KV selection

Choice of Verification Utterance • Why use identity claim? • One shorter dialog step • 80% of users claim and verify in one step • Why use common? • Many users do not like to speak their identity claim in public • Identity theft • Allow option to touch-tone identity claim • Multiple options for Identification • Enrollment very complex and long • Common utterance performance more predictable • Out-of-the-box performance better understood • ID claim may vary in length • Evaluating performance with identity claim more complex • Impostors MUST speak same text as enrollee • Identity claim -> Need live impostors

3 Enrollment utterances instead of 2: 1-3% lower automation 1 Verification utterance instead of 2: 1-3% lower automation 2. Collect enough data during enrollment and verification SSN/Account# SSN/Account# Authentication 1-9 1-9 1-9 1-9 KV 1-9 KV selection

Same verification performance as with 2 required utterances 3. Use variable length verification SSN/Account# SSN/Account# Authentication 1-9 80% 1-9 1-9 10% 1-9 1-9 KV selection

Examples: PIN, Secret Date Verifier not turned on Increases Automation Increases Effectiveness of Adaptation KV 10% 4. Use knowledge verification SSN/Account# SSN/Account# Authentication 1-9 80% 1-9 1-9 10% 1-9 1-9 KV selection

5. Use speaker adaptation SSN/Account# SSN/Account# Authentication 1-9 1-9 1-9 1-9 KV 1-9 KV selection

Speaker Verification Performance • Speaker Adaptation • Online: Score very well, adapt and get even better • Manual: Unsure, backoff to knowledge, adapt if knowledge passes • Cross-channel

Thank You! • www.nuance.com

Effective Design Strategies for Voice Authentication Systems

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