DNA cryptography is a field of study within DNA computing that focuses on using DNA as an information carrier and employing mathematical operations to convert plaintext into ciphertext.

Here's how DNA cryptography techniques generally work:

1. DNA as an Information Carrier:

   • DNA is a biological macromolecule made up of nucleotides.
   • Each nucleotide contains a single base, and there are four types of bases: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
   • These four bases are the fundamental alphabets used in DNA cryptography.
   • DNA usually exists as double-stranded molecules, with complementary bases (A with T, and C with G) held together by hydrogen bonds to form a double helix structure.

2. Encoding and Decoding Operations:

   • A common method involves converting plaintext into binary numbers.
   • These binary numbers are then converted into equivalent DNA nucleotide sequences.
   • The four basic units of DNA are encoded into binary in a specific manner:
   • Conversely, for decoding, DNA nucleotides can be converted back into numbers:

3. DNA Cryptography Techniques:

   • Several DNA-based encryption methods have been designed, including:

4. Reference Sequence Selection:

   • A key aspect of some DNA cryptography techniques is the secret selection of a "reference sequence" (S) from publicly available DNA sequences. This reference sequence is known only to the sender and the receiver.
   • The sender transforms this chosen DNA sequence (S) into a new sequence (S') by incorporating the secret message (M).
   • The transformed sequence (S') is then sent to the receiver along with many other DNA sequences.
   • The receiver examines all received sequences, identifies S', and recovers the secret message (M).

By combining these methods, DNA cryptography aims to increase encryption complexity and provide a secure way to transmit information.