نهان‌نگاری در رایانامه با ظرفیت نامحدود از طریق لغت‌نامه

هدف اصلی در نهان zwj;نگاری پنهان zwj;سازی یک پیام مخفی با قراردادن آن پیام در یک رسانه پوشانه است؛ به‌نحوی که کمینه تغییرات در رسانه ایجاد شده و آن تغییرات به‌راحتی قابل درک نباشد. رسانه پوشانه می zwj;تواند یک بستر قابل دسترس توسط عموم نظیر متن، رایانامه، صوت، تصویر یا ویدئو باشد. با گسترش استفاده از رایانامه در بین کاربران اینترنتی، ارائه روش zwj;های نهان zwj;گاری در بستر رایانامه مورد توجه قرار گرفته است؛ ولی روش zwj;های موجود دارای محدودیت در ظرفیت نهان zwj;نگاری بوده و به‌طور‌عمومی مصالحه zwj;ای بین امنیت و ظرفیت نهان zwj;نگاری در نظر می zwj;گیرند. در این مقاله یک روش نوین برای نهان‌نگاری رایانامه ارائه شده است که مبتنی بر لغت‌نامه بوده و هم‌زمان ظرفیت نامحدود و امنیت بالایی را ارائه می‌کند. در گام نخست روش پیشنهادی، پیام به‌وسیله یک لغت‌نامه فشرده و رمز‌شده و سپس به یک رشته‌بیتی تبدیل می شود. در هر مرحله با توجه به تعداد نویسه‌های محتوای رایانامه، قسمتی از رشته انتخاب‌شده، معادل ده‌دهی آن محاسبه شده و سپس با توجه به کلیدهای موجود، با آن‌ها نشانی‌های رایانامه ساخته می zwj;شود. ظرفیت نهان‌نگاری نامحدود در روش پیشنهادی منجر به امکان مخفی‌سازی هر میزان پیام در متن پوشانه شده است. همچنین نتایج آزمایش‌ها نشان می‌دهد که استفاده از لغت‌نامه منجر به کاهش حجم پیام و همچنین کاهش تعداد نشانی‌های گیرنده به میزان حدودی 44 درصد در مقایسه با روش‌های موجود شده است. این مهم به‌طور مستقیم به افزایش سطح امنیت روش پیشنهادی کمک می‌کند.

A High Capacity Email Steganography Scheme using Dictionary

The expansion of the use of information exchange space and public access to communication networks such as the Internet has led to the growing dependence of social institutions on the use of these networks. However, maintaining the security of information exchanged on networks is one of the most important challenges for users of these networks. One way to protect this data is to use private networks. But building these networks is not costeffective in terms of time and cost. In contrast, the use of encryption techniques, access control mechanisms and data concealment are among the effective solutions for security in the information exchange space.Existing methods for hiding information can be divided into three categories: cryptography, watermarking and steganography. In cryptography, a simple text is converted into encrypted text, which, of course, requires a decryption operation as well as an encryption key. In general, cryptographic techniques suffer from two major problems. The first problem is the ban on the transmission of encrypted data in dictatorial regimes, and the second problem is that cryptographers pay attention to encrypted data and stop any secret communication. The second category of information hiding methods is watermarking. Watermarking techniques are commonly used to protect the copyright of a digital content and to deal with issues such as fraud, fraud and copyright infringement in the data transfer space. In steganography methods, the transfer of information takes place in a cover through public communication channels, and only the sender and receiver are aware of the existence of a secret message. Two aspects of steganography must be observed. The first aspect is that the cover and secret content look the same in the face of statistical attacks. The second aspect is that the process of hiding the secret message in the cover is such that there is no difference between the cover and the secret in terms of the human perceptual system. In fact, the accuracy of the transmission media is maintained.Steganography methods use image, video, protocol, audio, and text platforms to hide information. Steganography in the text is difficult due to very little local variation. Humans are very sensitive to textual changes. Hence it is difficult to spell in the text. However, due to the high use of text in digital media, the insensitivity of text to compression, the need for less memory to store and communicate more easily and faster, many methods for steganography have been introduced in it. In addition, text is still one of the major forms of communication available to the general public around the world.In this paper, we propose a new email steganography scheme using a dictionarybased compression. In the proposed scheme, a number of email addresses containing a hidden message will be generated using the submitted text. The submitted text is sent to the generated and recipient addresses at the same time. This does not reveal the identity of the recipient of the message, and only the recipient can extract secret message using other email addresses. In the proposed method, two steganography keys are used. Using these two keys increases the security level of the proposed method. Also, the capacity of the proposed method is unlimited, which of course is a great advantage in a steganography method. This unlimited capacity provides high security for the proposed method. Another advantage is that the proposed method is not limited to the type of the covertext. Initially, the secret message is converted to a bit string by a dictionary. Then the operation of embedding the secret message in the recipient #39;s addresses is done by the steganography keys.The efficiency of steganography algorithms depends on various factors such as lack of detection by the human eye, lack of detection by statistical methods, and capacity. The proposed method does not change the covertext. Hence, this method is not detectable by humans or statistical methods. The capacity of the proposed method in this research is based on builtin email addresses. As the text of the message increases, the number of emails created increases too. Of course, this increase in the address of the emails created can lead to suspicion of the emails sent. Therefore, the parameter of the number of emails created is also important in the evaluation. In this paper, the efficiency of the proposed method is evaluated based on the two parameters and compared with existing methods. The results of this evaluation show that the proposed method, in addition to providing unlimited capacity in steganography, produces fewer email addresses generated as well as fewer message bits after compression.