A graph theoretic approach to steganography

Abstract. We suggest a graph-theoretic approach to steganography based on the idea of exchanging rather than overwriting pixels. We construct a graph from the cover data and the secret message. Pixels that need to be modified are represented as vertices and possible partners of an exchange are connected by edges. An embedding is constructed by solving the combinatorial problem of calculating a maximum cardinality matching. The secret message is then embedded by exchanging those samples given by the matched edges. This embedding preserves first-order statistics. Additionally, the visual changes can be minimized by introducing edge weights. We have implemented an algorithm based on this approach with support for several types of image and audio files and we have conducted computational studies to evaluate the performance of the algorithm

Watermark security via secret wavelet packet subband structures

Abstract. Wavelet packet decompositions generalize the classical pyramidal wavelet structure. We use the vast amount of possible wavelet packet decomposition structures to create a secret wavelet domain and discuss how this idea can be used to improve the security of watermarking schemes. Two methods to create random wavelet packet trees are discussed and analyzed. The security against unauthorized detection is investigated. Using JPEG and JPEG2000 compression we assess the normalized correlation and Peak Signal to Noise Ratio (PSNR) behavior of the watermarks. We conclude that the proposed systems show improved robustness against compression and provide around 2 1046 possible keys. The security against unauthorized detection is greatly improved.

Avaliação técnica e econômica de diferentes grupos genéticos de bovinos de corte machos superprecoces e do sistema de produção em confinamento Technical and economic evaluations of different genetic groups of yearling beef cattle males and of the feedlot production system

Avaliaram-se as variáveis técnicas e econômicas do sistema de produção em confinamento de 88 animais superprecoces (sete meses de idade) pertencentes a três grupos genéticos, com 23 animais Charolês x Nelore, 26 Red Angus x Nelore e 39 Abeerden Angus x Nelore. Foram registrados pesos no inicio do confinamento e ao abate, duração do confinamento, ganhos de peso no período e diário dos animais e, por meio de conceitos econômicos e operacionais, foram calculados os custos de produção. O modelo estatístico utilizado na análise das variáveis incluiu efeitos do grupo genético e do peso inicial como covariável. Não houve diferença entre grupos genéticos para peso ao abate e ganho de peso diário. A duração do confinamento foi menor para animais Charolês x Nelore (159 dias), intermediária para Red Angus x Nelore (170 dias) e maior para Abeerden Angus x Nelore (178 dias). Os custos total, operacional e variável da diária foram 1,02; 0,85 e 0,89 US$/dia, respectivamente. O confinador obteve lucro de 0,01 US$/kg e rentabilidade de 1,8%/mês. Não houve diferenças (P>0,05) entre grupos genéticos para custos, receita, margens bruta e líquida, lucro e rentabilidade.<br>This experiment was carried out to evaluate technical and economic parameters for feedlot production system of 88 seven-month-old animals of three genetic groups (23 Charolais x Nellore, 26 Red Angus x Nellore, and 39 Aberdeen Angus x Nellore). Production traits (initial and slaughtering weights, number of days in feedlot, and total and daily weight gains) were recorded and costs were estimated using operational and economic concepts. The statistical model used to analyze the traits included the fix effect of genetic group and initial body weight as a covariate. No differences were observed among the genetic groups for slaughtering weight and daily weight gain. Number of days in feedlot was low for Charolais x Nellore (159 days), intermediate for Red Angus x Nellore (170 days), and high for Aberdeen Angus x Nellore (178 days) animals. Total, operational, and variable costs were 1.02; 0.85; and 0.89 US$/day. Farmer profit was 0.01 US$/kg and profitability/month was 1.78%. Significant differences among the genetic groups were not observed for cost, income, gross and net margins, profit, and profitability

Exigências de proteína bruta e energia metabolizável em codornas de corte durante a fase de crescimento Protein and metabolizable energy requirements for meat type quail during the growing phase

Estudou-se a exigência de proteína bruta e energia metabolizável para codornas européias em crescimento, em cinco períodos experimentais, de sete dias cada. Foram utilizadas 384 codornas de ambos os sexos, com sete dias de idade em delineamento experimental utilizado inteiramente ao acaso, em esquema fatorial de 2&times;4, dois níveis de energia (2900 e 3100kcal de EM/kg de ração) e quatro níveis de proteína (22, 24, 26 e 28% de PB), com seis repetições de oito animais cada. Foram estudadas as variáveis ganho de peso (g), peso acumulado (g), consumo de ração (g) e conversão alimentar (g de ração/g de peso). Observou-se efeito linear dos níveis de proteína no primeiro período e quadrático nos demais períodos sobre o ganho de peso das aves. Os níveis de proteína foram estimados em 28,0% (2900kcal de EM/kg), 25,7% (3100kcal de EM/kg), 27,9%, 24,8% (3100kcal de EM/kg) e 23,1% (2900kcal de EM/kg) para o segundo, terceiro, quarto e quinto período, respectivamente.<br>Crude protein (CP) and metabolizable energy (ME) levels during five experimental periods of seven days each of the growing phase for European quail were determined. A total of 384 quails of both sexes were used in a completely randomized design in a 2&times;4 (energy and crude protein) factorial treatment with six replications of eight quails each. The metabolizable energy levels were 2900 and 3000kcal of ME/kg of diet and the crude protein levels were 22, 24, 26 and 28%. The analyzed variables were weight gain (g), accumulated weight (g), feed consumption (g), feed:gain ratio (g/g). Performance responses were evaluated by linear and quadratic regression of the traits on crude protein levels. Higher weight gains from the following protein and metabolizable energy levels combinations: 28.0% PB and 2900 kcal EM/kg (first period); 25.7% CP and 3100kcal ME/kg (second period); 27.9% and 2900kcal ME/kg (third period); 24.8% PB and 3100kcal/kg (fourth period) and 23.1% CP and 2900kcal/kg (fifth period)