Kriptografi ve stenografi yöntemlerini birlikte kullanarak yüksek güvenlikli veri gizleme

Yıl 2015, Cilt: 31 Sayı: 2, 115 - 123, 01.04.2015

Cemal Koçak

Öz

İletişimin gizliliğinde ve güvenli mesaj iletiminde kullanılan iki önemli teknik Kriptografi ve Steganografidir. Bu iki yöntemin birlikte kullanılması veri güvenliğini artırmaktadır. Kriptografide gizli bir mesaj şifrelenir, Steganografide ise mesaj, görüntü veya ses dosyaları içine yerleştirilir. Bu çalışmada Kriptografi ve Stenografi birleştirilerek hibrit bir model sunulmakta ve bu model için ise bir ara yüz tasarımı gerçekleştirilmektedir. Kriptografide, kullanıcının belirleyeceği anahtar kelime ile şifrelenecek metin bir matris oluşturularak şifrelenmiştir. Şifreli metnin resim içine gizlenmesi aşamasında güvenlik katmanı olarak ikinci şifre girilmesi sağlanmıştır. Şifrelenecek metin gerçek renkli RGB görüntü içine sadece “Kırmızı” ve “Yeşil” kanallarının en az değerlikli 2 biti değiştirilerek gizlenmiştir. Toplamda 4 bit değiştirilerek resme saklanabilecek şifreli metin boyutunda artış sağlanmıştır. Çalışmada kullanılan taşıyıcı resimler 24 bit/pixsel renk seviyeli olarak belirlenmiştir. Bu çalışmada stego görüntülerin kaliteleri Tepe Sinyal-Gürültü Oranı (Peak Signal-to-Noise Ratio-PSNR) ve Yapısal Benzerlik Endeksi (SSIM) ölçüm kriterlerine göre değerlendirilmiştir.

Anahtar Kelimeler

Yüksek kapasiteli veri gizleme, Kriptografi, Steganografi, PSNR, SSIM

High-capacity data hiding scheme together using cryptography and steganography

Öz

Cryptography and steganography are the two significant techniques used in security of communication and in safe message transfer. These two methods are applied together to improve data reliability. In cryptography, a secret message is encrypted, and in Steganography the message is placed into image, or voice files. In this study, a hybrid model is proposed by combining, cryptography and steganography and an interface is designed for proposed model. In cryptography, the text to be encrypted with a keyword determined by user is encoded by creating a matrix. While hiding an encrypted text into the picture, a second password is required to increase security. The text to be encrypted in true color RGB image are hidden by changing the least significant 2 bits of "red" and "green" channels. Size of the encrypted secret message has been increased by changing 4 bits in totally. The carrier pictures utilized in this study have been determined as 24 bit/pixel color scale. In this study, quality of the stego images has been evaluated according to the quality measurement criteria of Peak Signal-to-Noise Ratio (PSNR-dB) and Structural Similarity Index (SSIM).

Anahtar Kelimeler

High-Capacity, Scheme, Cryptography, Steganography, PSNR, SSIM

Kaynakça

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