crypto: add generic SipHash-1-3-UJ

diff --git a/src/crypto/siphash.cpp b/src/crypto/siphash.cpp
index 4c3f3b9d..333fad27 100644
--- a/src/crypto/siphash.cpp
+++ b/src/crypto/siphash.cpp
@@ -49,6 +49,23 @@ uint64_t CSipHasher::Finalize() const
                   .Finalize4();
 }
 
+SipHasher13UJ& SipHasher13UJ::Write(uint64_t data) noexcept
+{
+    m_state.Compress1(data);
+    return *this;
+}
+
+SipHasher13UJ& SipHasher13UJ::WriteJumbo(const uint256& hash) noexcept
+{
+    m_state.Compress1Jumbo(hash);
+    return *this;
+}
+
+uint64_t SipHasher13UJ::Finalize() const noexcept
+{
+    return m_state.Copy().Finalize3U();
+}
+
 uint64_t PresaltedSipHasher::operator()(const uint256& val) const noexcept
 {
     return m_state.Copy()
diff --git a/src/crypto/siphash.h b/src/crypto/siphash.h
index 5bcc6d45..0d17726c 100644
--- a/src/crypto/siphash.h
+++ b/src/crypto/siphash.h
@@ -20,6 +20,9 @@ class SipHashState
     static constexpr uint64_t C0{0x736f6d6570736575}, C1{0x646f72616e646f6d}, C2{0x6c7967656e657261}, C3{0x7465646279746573};
     /** SipHash v2 finalizer constant. */
     static constexpr uint64_t FINALIZER{0xFF};
+    /** SipHash custom unpadded finalizer constant. */
+    static constexpr uint64_t FINALIZER_UNPADDED{0x6465646461706e75};
+    static_assert(FINALIZER_UNPADDED != FINALIZER);
 
     /** Construct a SipHashState with the specified values as state. */
     ALWAYS_INLINE SipHashState(uint64_t v0, uint64_t v1, uint64_t v2, uint64_t v3) noexcept : m_v0{v0}, m_v1{v1}, m_v2{v2}, m_v3{v3} {}
@@ -43,6 +46,23 @@ public:
     explicit ALWAYS_INLINE SipHashState(uint64_t k0, uint64_t k1) noexcept : SipHashState{C0 ^ k0, C1 ^ k1, C2 ^ k0, C3 ^ k1} {}
     /** Construct a copy of this state. */
     ALWAYS_INLINE SipHashState Copy() const noexcept { return {m_v0, m_v1, m_v2, m_v3}; }
+    /** Mutably compress one block into this state, with 1 SipRound. */
+    ALWAYS_INLINE SipHashState& Compress1(uint64_t data) noexcept
+    {
+        m_v3 ^= data;
+        SipRound();
+        m_v0 ^= data;
+        return *this;
+    }
+    /** Mutably compress one jumbo block into this state, with 1 SipRound. */
+    ALWAYS_INLINE SipHashState& Compress1Jumbo(const uint256& data) noexcept
+    {
+        const uint64_t d0{data.GetUint64(0)}, d1{data.GetUint64(1)}, d2{data.GetUint64(2)}, d3{data.GetUint64(3)};
+        m_v3 ^= d0; m_v0 ^= d1; m_v1 ^= d2; m_v2 ^= d3;
+        SipRound();
+        m_v0 ^= d0; m_v1 ^= d1; m_v2 ^= d2; m_v3 ^= d3;
+        return *this;
+    }
     /** Mutably compress one block into this state, with 2 SipRounds. */
     ALWAYS_INLINE SipHashState& Compress2(uint64_t data) noexcept
     {
@@ -62,6 +82,16 @@ public:
         SipRound();
         return m_v0 ^ m_v1 ^ m_v2 ^ m_v3;
     }
+    /** Mutably finalize this state with 3 SipRounds using the unpadded finalizer, and return the
+     *  resulting hash. */
+    ALWAYS_INLINE uint64_t Finalize3U() noexcept
+    {
+        m_v2 ^= FINALIZER_UNPADDED;
+        SipRound();
+        SipRound();
+        SipRound();
+        return m_v0 ^ m_v1 ^ m_v2 ^ m_v3;
+    }
 };
 
 /** General SipHash-2-4 implementation. */
@@ -85,6 +115,62 @@ public:
     uint64_t Finalize() const;
 };
 
+/** A custom weaker variant of SipHash-1-3 without padding, and supporting "jumbo" inputs.
+ *
+ * Compared to the traditional SipHash-2-4, this incorporates 3 changes:
+ *
+ * - Use SipHash-1-3: This common variant reduces the number of rounds between input blocks from 2
+ *                    to 1, and the number of finalization rounds at the end from 4 to 3.
+ *                    It is a standard faster choice with weaker security guarantees. It is
+ *                    considered strong enough for use in hash tables and other applications with
+ *                    only weak security requirements, in particular when attackers cannot directly
+ *                    observe the hash function output, and cannot control k0 and k1.
+ *
+ * - Remove padding: Standard SipHash operates on byte-oriented inputs, which are converted into
+ *                   8-byte blocks internally by adding a padding of 1-8 bytes to obtain a multiple
+ *                   of 8 bytes. In this variant, the input is a sequence of blocks instead, which
+ *                   are used without padding. This saves 1 round for inputs that are a multiple of
+ *                   8 bytes already. The padding normally adds a commitment to the input's byte
+ *                   length, but since our input is block oriented, and there is one round per
+ *                   input, the function of that commitment is directly fulfilled by the number of
+ *                   rounds. The empty input is permitted; it yields the result of finalizing the
+ *                   initialization directly. Out of an abundance of caution the finalizing
+ *                   v2 ^= 0xff is changed to v2 ^= 0x6465646461706e75 ("unpadded" in LE64), to
+ *                   avoid collisions between standard SipHash-1-3 and this variant.
+ *
+ * - Jumbo blocks: We generalize the input to consist of a sequence of blocks which are each either
+ *                 exactly 8 bytes (normal blocks) or 32 bytes (jumbo blocks), and may be
+ *                 arbitrarily mixed. For hash-table use, cryptographic hash outputs must make up
+ *                 all but a small bounded number of retained jumbo blocks. Note that the block
+ *                 structure matters: hashing one jumbo block is not the same as hashing the same
+ *                 data split up into four normal blocks. Jumbo blocks are interpreted as 4 LE64 integers
+ *                 (d0,d1,d2,d3), and XOR'ed into the state before a round as
+ *                 (v0,v1,v2,v3) ^= (d1,d2,d3,d0), and XOR'ed into the state after a round as
+ *                 (v0,v1,v2,v3) ^= (d0,d1,d2,d3). This is a strict generalization of normal block
+ *                 processing, in the sense that if d1..d3=0, it is identical to processing a normal
+ *                 block d0 (a single LE64 integer). Of course, making d1..d3=0 should be impossible
+ *                 in the output of a cryptographic hash function. These jumbo blocks are acceptable
+ *                 because even though they may give the attacker more control within a single
+ *                 round, that control is limited by the cryptographic hash in between.
+ *
+ * Other components are unchanged: initialization constants, SipRound, and 64-bit output.
+ * This interface serves as an executable specification for fixed-width implementations.
+ */
+class SipHasher13UJ
+{
+    SipHashState m_state;
+
+public:
+    /** Construct a SipHash-1-3-UJ calculator initialized with 128-bit key (k0, k1). */
+    SipHasher13UJ(uint64_t k0, uint64_t k1) noexcept : m_state{k0, k1} {}
+    /** Hash a normal 64-bit value. */
+    SipHasher13UJ& Write(uint64_t data) noexcept;
+    /** Hash a 256-bit value as a jumbo block. For hash-table use, non-hash inputs must remain few and bounded. */
+    SipHasher13UJ& WriteJumbo(const uint256& hash) noexcept;
+    /** Compute the 64-bit SipHash-1-3-UJ of the data written so far. The object remains untouched. */
+    uint64_t Finalize() const noexcept;
+};
+
 /**
  * Optimized SipHash-2-4 implementation for uint256.
  *