policy

var (
	// AdvertiseCipherPreferences is added to the self signature to tell
	// others which symmetric ciphers (in order) that we prefer to receive.
	//
	// When a client is choosing a cipher to use, it looks for the
	// strongest supported by *all* recipients, and it falls back to
	// TripleDES *even* if that's no-one's preferences.
	//
	// This is equivalent to this GnuPG config from Riseup's OpenPGP
	// best practice:
	//
	// > personal-cipher-preferences AES256 AES192 AES CAST5
	//
	// https://tools.ietf.org/html/rfc4880#section-9.2
	// https://help.riseup.net/en/security/message-security/openpgp/best-practices
	AdvertiseCipherPreferences = []uint8{
		symmetric.AES256,
		symmetric.AES192,
		symmetric.AES128,
		symmetric.CAST5,
	}

	// AcceptablePreferredSymmetricAlgorithms defines what combinations of
	// symmetric key ciphers we consider OK (e.g. we don't warn about).
	// Note that the order of algorithms matters, e.g. {AES256, CAST5} is
	// different from {CAST5, AES256}
	AcceptablePreferredSymmetricAlgorithms = [][]uint8{
		[]uint8{symmetric.AES256, symmetric.AES192, symmetric.AES128, symmetric.CAST5},
		[]uint8{symmetric.AES256, symmetric.AES192, symmetric.AES128},
	}

	// SupportedSymmetricKeyAlgorithms defines what algorithms we can
	// technically decrypt (but doesn't mean they're encouraged.)
	SupportedSymmetricKeyAlgorithms = []uint8{
		symmetric.AES128,
		symmetric.AES192,
		symmetric.AES256,
		symmetric.CAST5,
		symmetric.TripleDES,
	}

	// AdvertiseCompressionPreferences is added to the self signature to tell others
	// which compression (in order) that we prefer to use. Note that Golang
	// doesn't support BZIP, so we don't specify that.
	//
	// Riseup's OpenPGP best practice settings specify:
	//
	// > default-preference-list [...] ZLIB BZIP2 ZIP Uncompressed
	//
	// https://tools.ietf.org/html/rfc4880#section-9.3
	AdvertiseCompressionPreferences = []uint8{
		compression.ZLIB,
		compression.ZIP,
		compression.Uncompressed,
	}

	// AdvertiseHashPreferences is added to the self signature to tell
	// others which hashes (in order) that we prefer to use.
	//
	// Note that clients implicity support SHA1 if no other digest is
	// available.
	//
	// Riseup's OpenPGP best practice settings specify:
	//
	// > personal-digest-preferences SHA512 SHA384 SHA256 SHA224
	//
	// https://tools.ietf.org/html/rfc4880#section-9.4
	AdvertiseHashPreferences = []uint8{
		hash.Sha512,
		hash.Sha384,
		hash.Sha256,
		hash.Sha224,
	}

	// AcceptablePreferredHashAlgorithms defines what combinations of
	// hash algorithms we consider OK (e.g. we don't warn about).
	// Note that the order of algorithms matters, e.g. {SHA256, RIPEMD160}
	// is different from {RIPEMD160, SHA256}
	AcceptablePreferredHashAlgorithms = [][]uint8{
		[]uint8{hash.Sha512, hash.Sha384, hash.Sha256, hash.Sha224},
		[]uint8{hash.Sha512, hash.Sha384, hash.Sha256, hash.Sha224, hash.Ripemd160},
	}

	// SupportedHashAlgorithms defines what hash algorithms we can
	// technically support (but doesn't mean they're encouraged.)
	SupportedHashAlgorithms = []uint8{
		hash.Md5,
		hash.Sha1,
		hash.Ripemd160,
		hash.Sha224,
		hash.Sha256,
		hash.Sha384,
		hash.Sha512,
	}

	// AcceptableSignatureHashes defines the hash functions we consider
	// acceptable for self signatures (on UIDs) and subkey binding
	// signatures.
	AcceptableSignatureHashes = []crypto.Hash{
		crypto.SHA512,
		crypto.SHA256,
		crypto.SHA384,
		crypto.SHA224,
	}

	// SignatureHashFunction is the hash algorithm used for generating
	// subkey binding signatures and self signatures.
	SignatureHashFunction = crypto.SHA512
)