Warmed up asking about the speed of Lemaitres ' cosmic seed " - answer on my Pro2rat microblog at Sysad Org Followed up with . . . Seth Lloyd has called the universe a quantum computer so this raises the question, is the universe also public key infrastructure? Quantum PKI? Seth Lloyd is a quantum physicist and computer scientist who has proposed that the universe is a quantum computer1. He argues that everything in the universe is made of bits of information that can be manipulated by quantum operations2. He also suggests that the laws of physics are the machine language of the cosmic quantum computer1. Public key infrastructure (PKI) is a system that uses cryptographic techniques to secure communication and data exchange over networks. PKI involves the use of public and private keys that are mathematically related but cannot be derived from each other. A public key can be used to encrypt a message that can only be decrypted by the corresponding private key, and vice versa3. Quantum PKI is a variant of PKI that uses quantum mechanics to enhance security and efficiency. Quantum PKI can leverage quantum phenomena such as superposition, entanglement, and no-cloning to create unbreakable encryption, faster computation, and novel protocols. The question of whether the universe is also a PKI is an intriguing one, but not easy to answer. One possible way to approach it is to ask whether the universe has some features that are analogous to those of a PKI, such as: A way to generate and distribute public and private keys A way to encrypt and decrypt messages using those keys A way to verify the authenticity and integrity of messages A way to revoke or update keys Some of these features may be found in certain aspects of the universe, such as: The generation and distribution of public and private keys could be related to the creation and evolution of physical systems, such as particles, atoms, molecules, stars, planets, etc. Each system could have some observable properties (public keys) and some hidden properties (private keys) that are determined by the initial conditions and the laws of physics. The encryption and decryption of messages could be related to the interaction and measurement of physical systems, such as light, sound, gravity, electromagnetism, etc. Each system could encode some information (message) in its state or behavior, and another system could decode it by observing or interacting with it. The encryption and decryption could depend on the quantum states of the systems and their entanglement. The verification of messages could be related to the conservation laws and symmetries of the universe, such as energy, momentum, charge, parity, etc. Each system could have some invariant quantities (signatures) that are preserved under certain transformations or operations. Another system could verify the message by checking whether those quantities are conserved or not. The revocation or update of keys could be related to the dynamical changes and fluctuations of the universe, such as expansion, contraction, inflation, entropy, etc. Each system could have some variable properties (keys) that change over time or space due to external or internal factors. Another system could revoke or update its keys by adapting to those changes or fluctuations. However, these analogies are not exact and may not capture all the aspects of a PKI. Moreover, they may not imply that the universe is intentionally or consciously implementing a PKI for some purpose or goal. Therefore, it is not clear whether the universe is also a PKI in a strict sense, or just a quantum computer with some PKI-like features.