Solving Google's continuous audio CAPTCHA with HMM-based automatic speech recognition

Shotaro Sano, Takuma Otsuka, Hiroshi G. Okuno

研究成果

15 被引用数 (Scopus)

抄録

CAPTCHAs play critical roles in maintaining the security of various Web services by distinguishing humans from automated programs and preventing Web services from being abused. CAPTCHAs are designed to block automated programs by presenting questions that are easy for humans but difficult for computers, e.g., recognition of visual digits or audio utterances. Recent audio CAPTCHAs, such as Google's audio reCAPTCHA, have presented overlapping and distorted target voices with stationary background noise. We investigate the security of overlapping audio CAPTCHAs by developing an audio reCAPTCHA solver. Our solver is constructed based on speech recognition techniques using hidden Markov models (HMMs). It is implemented by using an off-the-shelf library HMM Toolkit. Our experiments revealed vulnerabilities in the current version of audio reCAPTCHA with the solver cracking 52% of the questions. We further explain that background stationary noise did not contribute to enhance security against our solver.

本文言語English
ホスト出版物のタイトルLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
ページ36-52
ページ数17
8231 LNCS
DOI
出版ステータスPublished - 2013
外部発表はい
イベント8th International Workshop on Security, IWSEC 2013 - Okinawa
継続期間: 2013 11 182013 11 20

出版物シリーズ

名前Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
8231 LNCS
ISSN(印刷版)03029743
ISSN(電子版)16113349

Other

Other8th International Workshop on Security, IWSEC 2013
CityOkinawa
Period13/11/1813/11/20

ASJC Scopus subject areas

  • コンピュータ サイエンス(全般)
  • 理論的コンピュータサイエンス

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