title: Compression and cryptology

authors: Irvine, Sean A.

abstract: Currently data compression and encryption are carried out as two separate activities. A simpler communication system would result if these two activities could be combined. The security properties of lossless data compression techniques are investigated. It is argued that compression is necessary for security but demonstrated that current compression techniques are not sufficient. Both coding techniques (arithmetic coding and Huffman coding) and modelling techniques (splaying, Ziv-Lempel, and prediction by partial matching—PPM) are examined. It is shown that all these systems have significant security flaws. Explicit attacks are given and descriptions of algorithms to automate the attacks are provided. Chosen plaintext attacks are given for Huffman coding, PPM, and splaying. Known plaintext attacks are given for arithmetic coding, splaying and Ziv-Lempel compressors. A ciphertext only attack is given for the Ziv-Lempel compressors. These results are used to highlight why better models of natural languages have important applications in cryptology. In particular, it is explained how a better model of a source leads naturally to increased resistance from dictionary and ciphertext only attacks. 

Some of the attacks presented involve novel methods not previously reported in the literature. In particular, it is shown how a backtracking search can be used for known and chosen plaintext attacks against fixed to variable length binary encoders (Huffman coding and splaying). It is shown how a good model of the source (a PPM model) can be used in an automatic ciphertext only attack against simple substitution ciphers and Ziv-Lempel compressors. The attack against simple substitution ciphers is at least comparable to previously published automated approaches. In some cases analytical or asymptotic results concerning the complexity of the attacks are given. It appears that compression leads naturally to increased ciphertext only resistance, but current compressors contain no operations likely to thwart known or chosen plaintext attacks.

text: Compression and cryptology Currently data compression and encryption are carried out as two separate activities. A simpler communication system would result if these two activities could be combined. The security properties of lossless data compression techniques are investigated. It is argued that compression is necessary for security but demonstrated that current compression techniques are not sufficient. Both coding techniques (arithmetic coding and Huffman coding) and modelling techniques (splaying, Ziv-Lempel, and prediction by partial matching—PPM) are examined. It is shown that all these systems have significant security flaws. Explicit attacks are given and descriptions of algorithms to automate the attacks are provided. Chosen plaintext attacks are given for Huffman coding, PPM, and splaying. Known plaintext attacks are given for arithmetic coding, splaying and Ziv-Lempel compressors. A ciphertext only attack is given for the Ziv-Lempel compressors. These results are used to highlight why better models of natural languages have important applications in cryptology. In particular, it is explained how a better model of a source leads naturally to increased resistance from dictionary and ciphertext only attacks. 

Some of the attacks presented involve novel methods not previously reported in the literature. In particular, it is shown how a backtracking search can be used for known and chosen plaintext attacks against fixed to variable length binary encoders (Huffman coding and splaying). It is shown how a good model of the source (a PPM model) can be used in an automatic ciphertext only attack against simple substitution ciphers and Ziv-Lempel compressors. The attack against simple substitution ciphers is at least comparable to previously published automated approaches. In some cases analytical or asymptotic results concerning the complexity of the attacks are given. It appears that compression leads naturally to increased ciphertext only resistance, but current compressors contain no operations likely to thwart known or chosen plaintext attacks.

year: 1997

title: Predator free New Zealand by 2050 - Benefits for the lakes

authors: Kessick, Martin

abstract: I am here today to speak to you about Predator Free 2050 and the benefits of this programme for the lakes. I am a new Deputy Director-General and only been in my role for 7 weeks and that is because the biodiversity business group that I now lead has only recently been formed. I am accountable for the delivery of the Department’s science technical monitoring and reporting functions and this is the first time these functions have been brought into one business group within the department, which is enabling us to have a fantastic focus on our national biodiversity work.

text: Predator free New Zealand by 2050 - Benefits for the lakes I am here today to speak to you about Predator Free 2050 and the benefits of this programme for the lakes. I am a new Deputy Director-General and only been in my role for 7 weeks and that is because the biodiversity business group that I now lead has only recently been formed. I am accountable for the delivery of the Department’s science technical monitoring and reporting functions and this is the first time these functions have been brought into one business group within the department, which is enabling us to have a fantastic focus on our national biodiversity work.

year: 2017

title: Researching the Process of Auahi Kore for Marae

authors: Masters-Awatere, Bridgette

abstract: • The current report is piece of a qualitative research exploring issues relating the development of Marae Auahi Kore. Such aspects as; factors that aid or impede the process, resources available or required by marae, and people's perceptions of the Auahi Kore brand were explored.

• Interviews were conducted with people from a variety of backgrounds. Research participants included: Marae Trustees, Public Health Workers, Runanga Staff as well as Kaumatua and Kuia. These people were identified as key informants for the current project. A total of 25 people were interviewed during March and April using an open interview schedule.

• Exploration into the Smokefree policies of marae was not pursued within the current project as this was not the focus nor the intent of the research. Project constraints such as time and budget meant there was a limit to what could be undertaken for the current piece of research.

text: Researching the Process of Auahi Kore for Marae • The current report is piece of a qualitative research exploring issues relating the development of Marae Auahi Kore. Such aspects as; factors that aid or impede the process, resources available or required by marae, and people's perceptions of the Auahi Kore brand were explored.

• Interviews were conducted with people from a variety of backgrounds. Research participants included: Marae Trustees, Public Health Workers, Runanga Staff as well as Kaumatua and Kuia. These people were identified as key informants for the current project. A total of 25 people were interviewed during March and April using an open interview schedule.

• Exploration into the Smokefree policies of marae was not pursued within the current project as this was not the focus nor the intent of the research. Project constraints such as time and budget meant there was a limit to what could be undertaken for the current piece of research.

year: 2000