Sharif Digital Repository

The mobile phone is one of the technologies which are widely used these days. It is available in most countries and all people, even children and elderly people can use it. It seems that in the near future, each person will have at least one mobile phone. So it is a good choice for communication in emergency situations, such as a heart attack or after an earthquake. In this chapter, we will survey a number of systems which are designed for communication in emergency situations and then explain three systems which are developed by the authors. The first one is for locating and rescuing victims after an earthquake. The second system is for calling an emergency team by patients in emergency... 

Embedding a secret message into a cover media without attracting any attention, known as steganography, is one of the methods used for hidden communication purposes. One of the cover media that can be used for steganography is speech. In this study, the authors propose a new steganography method in speech signals. In this method, the silence intervals of speech are found and the length (number of samples) of these intervals is changed to hide information. The main feature of our method is robustness to MPEG-1 layer III (MP3) compression. This method can hide information in a speech stream with very low processing time which makes it a real-time steganography method. The hiding capacity of... 

Digital music is now widely used and a great number of digital music files are available on the Internet. Designing systems that can automatically index, search and retrieve the digital music is one of the active research fields. One of the requirements for design and evaluation of such systems is corpuses of digital music samples. A good corpus is expected to have a number of features such as including a great number of samples, have samples of different artists and also samples with different quality. Additionally, the regional music of different parts of the world uses local musical instruments which results in music that are acoustically different. So, corpuses of regional music are... 

Feedback vibration is a standard feature in almost every home video game console controller to vibrate in selected circumstances, such as when the user's character kick the ball or hit the opponent, to immerse the player in the game. In the handheld game consoles this feature causes the handheld game consoles to vibrate. But the handheld game consoles are different than home video game consoles. In this paper we examine the suitability of using feedback vibration in the handheld game consoles. We evaluated feedback vibration popularity among the users. We used Nintendo DS handheld game consoles for this evaluation  

Watermarking is the process of hiding information in a media and usually used to for copyright protection. In software watermarking, the information is added to the source code of program and can be extracted from compiled executable code. In this paper, a new software watermarking algorithm is proposed by equation reordering. In this method, the order of operands in an equation is changed according to the information we want to hide in a way that the result of the equation is unchanged. One of the main advantages of this method is that no code added to the program, so the size and speed of the program not changed  

One of the methods introduced for establishing hidden communication is steganography. Steganography is the art of hiding information in a cover media without attracting attention. Text documents are one of the common cover media used for steganography in past. Steganography in text is more difficult than other media because there is a little redundant information in text documents. In this study, we propose a high capacity text steganography method. Our method can hide about 400 bits in each kilobyte of text. In Persian and Arabic, each letter can have four different shapes regarding to its position in the word. In this method this feature of Persian and Arabic languages is used for... 

Registration websites use CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart) systems to prevent the bot programs from wasting their resources. But sometimes the CAPTCHA test is difficult for human users to pass because the users have different ages, languages, etc. In this paper we propose a solution for this problem. The registration system can select a kind of CAPTCHA system among different available CAPTCHA systems regarding to the user's needs such as user language and disabilities. For example if the user has non-English language, the system chooses a CAPTCHA method which does not need English language knowledge. © 2008 IEEE  

Nowadays the Internet users are from different ages and groups. The disabled people also use the Internet. Some websites are especially created for disabled people. Many Internet sites offers services for human users, but unfortunately some computer programs are designed to abuse these services. To solve this problem, some systems named CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart) have been introduced to distinguish between human users and computer programs. CAPTCHA methods are mainly based on the weaknesses of OCR systems while using them is undesirable for human users, especially for disabled people. Therefore some CAPTCHA methods are designed... 

Steganography is a method for hidden exchange of information by hiding data in a cover media such as image or sound. Text Steganography is one of the most difficult methods because a text file is not a proper media to hide data in it. In this paper we propose a new text Steganography method. In this method, we hide data in TeX documents. This method hides the data in places where there is a ligature such as "fi". © 2008 IEEE  

In some websites, it is necessary to distinguish between human users and computer programs which is known as CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart). CAPTCHA methods are mainly based on the weaknesses of OCR systems while using them are undesirable to human users and cannot be used in some devices such as devices without keyboard. Nintendo DS is a popular handheld game console which was released in 2004. Nowadays, facilities such as the Internet connection are added in new game consoles and they are not merely used for playing games. Nintendo DS is also capable of connecting to the Internet by using the Nintendo DS Browser. But Nintendo DS Browser... 

Sending information secretly and communicating covertly have been of great interest for ages. On the other hand, text documents have been widely used and consequently various methods for hiding information in texts (Text Steganography) have been developed so far. In this paper a new method is proposed to hide information in digital Persian and Arabic Unicode texts. In Persian and Arabic, each letter can have four different shapes regarding to its position in the word. In this method by using this feature of Persian and Arabic languages and the way which documents are saved in the Unicode Standard, the information is hidden in Unicode text documents. This method has a good hiding capacity... 

Nowadays the Internet users are from different ages and groups. Disabled people are a group of the Internet users. Some websites are especially created for these people. One group of the disabled people are deaf persons. They have a special talking language which is named sign language. Here we present a method to encourage them, esp. children, to learn the sign language. In this method, when a deaf person wants to enter a website which is created for deaf persons, a word is shown as a movie using a sign language. The user should recognize the word and select it from a list. If the user understands the sign language and recognizes the word, he/she can enter the website. This project has been... 

In some websites it is necessary to distinguish between human users and computer programs which is known as CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart). CAPTCHA methods are mainly based on the weaknesses of OCR systems while using them are undesirable to human users. In this paper a new CAPTCHA method is introduced on the basis of showing a movie of a person's action. Then we ask the user to describe the movement of that person. The user should select the sentence which describes the motion from a list of sentences. If the user chooses the right sentence we can guess that the user is a human and not a computer program. The main advantage of this method... 

Today there are many Internet sites which require only the entry by human users but unfortunately some computer softwares called bots are designed by some hackers to enter these sites and use their resources through false registration. As a result some systems named CAPTCHA have been introduced to tell apart human users and computer software. This paper introduces a new CAPTCHA method. In this method a simple mathematical problem is generated according to a predefined pattern but instead of some object's name, we put their images. Then the whole problem is saved and shown to the user inform of an image to be answered by him. But since answering this problem requires four abilities of... 

Nowadays, many daily human activities such as education, commerce, talks, etc. are carried out through the Internet. In cases such as the registering in websites, some hackers write programs to make automatic false enrolments which waste the resources of the website while this may even stop the entire website from working. Therefore, it is necessary to tell apart human users from computer programs which is known as CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart). CAPTCHA methods are mainly based on the weak points of OCR (Optical Character Recognition) systems while using them are undesirable to human users. In this paper a method has been presented for... 

Nowadays the Internet users are from different ages and groups. The disabled people also use the Internet. Some websites are especially created for disabled people. Many Internet sites offers services for human users, but unfortunately some computer programs are designed which abuse these services. As a result some systems named CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart) have been introduced to tell apart human users and computer software. In this paper, a new CAPTCHA method is introduced which can be used by blindpeople. In this method a simple mathematicalproblem is created according to predefined patterns and converted to speech using a... 

In last 20 years, the Internet and mobile communication growth in parallel. There are many sites specially designed for mobile phones that users must enter username and password to enter them. In this paper we introduce a new method based on CAPTCHA which does not require entering any password. Instead of entering the password, an image of a number is shown to the user and he/she must type it. The user response is coded with his/her mobile phone IMEI and sent to the server. The server checks user's response according to user's IMEI and if it was correct, let the user to enter the site, so there is no need to enter any password. This method has been implemented in PHP and J2ME languages and... 

In some websites it is necessary to tell apart human users from computer programs which is known as CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart). CAPTCHA methods are mainly based on the weak points of OCR systems while using them are undesirable to human users. In this paper a method has been presented for telling the human users and computer softwares apart on the basis of choice of an object shown on the screen. In this method some objects are chosen randomly and the pictures about these topics are downloaded from Internet. Then after effecting some changes such as rotating, all of the pictures are shown on the screen. Then we ask the user to choose a... 

Nowadays, computer is being used in many aspects of human life. A consequence of computer is electronic documents. Computers can't understand written documents. So, we need to convert written documents to electronic documents in order to be able to process them with computers. One of the common methods for converting written texts to electronic text is Optical Character Recognition (OCR). A lot of work has been done on English OCR, but Persian/Arabic OCR is still under development. A phase which commonly used in recognition part of an OCR system is estimating font size of text. Usually when the font size of text is found, the pen width is calculated. The pen width can be used for character... 

Nowadays, many daily human activities such as education, commerce, talks, etc. are carried out through the Internet. In cases such as the registering in websites, some hackers write programs to make automatic false enrolments which waste the resources of the website while this may even stop the entire website from working. Therefore, it is necessary to tell apart human users from computer programs which is known as CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart). CAPTCHA methods are mainly based on the weak points of OCR (Optical Character Recognition) systems while using them are undesirable to human users and esp. difficult in tools such as PDA's or...