Abstract: Described implementations obtain credential information including an encrypted digital identity (ID). The encrypted digital ID may include a public component of a credential and identity data. Furthermore, the credential information may include cryptographically obfuscated data based on the identity data and a private component of the credential. A proof is obtained that includes proof data. The proof data may confirm that the credential information was correctly generated. Verification of the proof data, and confirmation that the cryptographically obfuscated data is not associated in a collection of cryptographically obfuscated data, cause a computer-implemented service to issue a pseudonym. The pseudonym is usable to generate a relationship associated with a computer-implemented service.

Abstract: Described implementations obtain a proof of valid attestation data. The attestation data may include configuration data of a host computing system. A prover service may receive the attestation data. The prover service may generate a proof to prove that the attestation data includes valid configuration data of the host computer system, without revealing sensitive or private information of the host computing system. The proof may be a zero-knowledge proof.

Abstract: A resource may be abused if its users incur little or no cost. For example, e-mail abuse is rampant because sending an e-mail has negligible cost for the sender. Such abuse may be discouraged by introducing an artificial cost in the form of a moderately expensive computation. Thus, the sender of an e-mail might be required to pay by computing for a few seconds before the e-mail is accepted. Unfortunately, because of sharp disparities across computer systems, this approach may be ineffective against malicious users with high-end systems, prohibitively slow for legitimate users with low-end systems, or both. Starting from this observation, we identify moderately hard, memory bound functions that most recent computer systems will evaluate at about the same speed, and we explain how to use them for protecting against abuses.

Abstract: A resource may be abused if its users incur little or no cost. For example, e-mail abuse is rampant because sending an e-mail has negligible cost for the sender. Such abuse may be discouraged by introducing an artificial cost in the form of a moderately expensive computation. Thus, the sender of an e-mail might be required to pay by computing for a few seconds before the e-mail is accepted. Unfortunately, because of sharp disparities across computer systems, this approach may be ineffective against malicious users with high-end systems, prohibitively slow for legitimate users with low-end systems, or both. Starting from this observation, we identify moderately hard, memory bound functions that most recent computer systems will evaluate at about the same speed, and we explain how to use them for protecting against abuses.