1, The full form of CHAP is Challenge-Handshake Authentication Protocol. It’s used on Computing ,Protocols in Worldwide

Challenge-Handshake Authentication Protocol (CHAP) is an identity verification protocol that does not rely on sending a shared secret between the access-requesting party and the identity-verifying party (the authenticator). CHAP is based on a shared secret, but in order to authenticate, the authenticator sends a “challenge” message to the access-requesting party, which responds with a value calculated using a “one-way hash” function that takes as inputs the challenge and the shared secret. The authenticator checks the response against its own calculation of the expected hash value.  If the values match, the authentication succeeds, otherwise it fails.  Following the establishment of an authenticated connection, the authenticator may send a challenge to the access-requesting party at random intervals, to which the access-requesting party will have to produce the correct response.

CHAP has built in measures to protect against playback attack by requiring the access-requesting party to use an incrementally changing identifier and a variable    challenge value. The authenticator is in control of the frequency and timing of the challenges. The use of repeated challenges is intended to limit the time of exposure to any single attack.

Features :

• It uses 3-way handshaking protocol (not like TCP). First, the authenticator sends a challenge packet to the peer then, the peer responds with a value using its one way hash function. The authenticator then matches the received value with its own calculated hash value. If the values match then the authentication is acknowledged otherwise, the connection will be terminated.
• It uses one-way hash function called MD5.
• It also authenticates periodically to check if the communication is taking place with the same device or not.
• Also, it provides more security than PAP (Password Authentication Procedure) as the value used (find out by hash function) is changed variably.
• CHAP requires to know the plaintext of the secret as it is never sent over the network.

2, The full form of CHAP is Community Health Accreditation Program. It’s used on Associations & Organizations ,Regional Organizations in United States

CHAP is an independent, nonprofit accrediting body for home and community-based health care organizations. We are people who care on a mission to lead and a journey to serve. Created in 1965 as a joint venture between the American Public Health Association and the National League for Nursing, CHAP was the first accrediting body for home and community-based health care organizations in the United States. We accredit a variety of home and community-based health care organizations that make high-quality care a programmatic and business priority. We bring deep insights, best practices and thought leadership to the organizations we serve, improving the care and services they provide.

Don’t just take our word for it; we’re a nationally approved accrediting organization and have “deeming” authority granted by the Centers for Medicare and Medicaid Services (CMS). We know more about home and community-based health care accreditation than anyone in the industry.

CHAP will be the standard bearer for excellence in health outcomes, person centered care and the health of the community.

CHAP defines, verifies and advances the highest quality of home and community-based care through its standards, accreditation, education and research.